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DENTAL    CHEMISTRY. 


CHEMISTRY 


METALLURGY 


AS  APPLIED  TO  THE 


STUDY  AND  PEACTICE  OF  DENTAL  SURGERY. 


BY 


A.   SNOWDENjPIGGOT,   M.  D., 


tATE  PROFESSOR  OF  ANATOMY  AND  PHYSIOLOGY  IN  THE  'WASHINGTON  UNTVERSITT  OF  BALTIMORE. 


WITH    NUMEROUS    ILLUSTRATIONS. 


PHILADELPHIA: 
LINDSAY    AND    BLAKISTON. 


Z< 


0 


Entered  according  to  the  Act  of  Congress,  in  the  year  1853,  by 
LINDSAY  AND  BLAKISTON, 

in  the  Office  of  the  Clerk  of  the  District  Court  of  the  United  States  in  and  for 
the  Eastern  Disti-ict  of  Pennsylvania. 


PHILADELPHIA  : 
T.   K.   AND  P.   G.  COLLINS,  PEIXTERS. 


'P 

TO 

CHxVriN  A.  IIAEEIS,  M.D.,  D.D.S., 

PROFESSOR  OF  THE  PRINCIPLES  AND  PRACTICE  OF  DENTAL  SURGERY  IX  IDE  BALTIMORE  COLLEGE, 

AS  A  TOKEN  OF  RESPECT 

FOR  HIS 

FROFESSIONAL  EMINENCE,  AND  ESTEEM  FOE  HIS  PRIVATE  WORTH, 

THIS  WORK 

IS   RESPECTFULLY   DEDICATED 

BY  HIS 
FRIEND  AND  OBEDIENT  SERVANT, 

THE  AUTHOR. 


PEEFACE. 


The  following  pages  were  written  at  the  suggestion  of  several 
eminent  dentists,  in  whose  judgment  on  all  subjects  pertaining 
to  dentistry,  and  especially  dental  education,  the  author  has  the 
fullest  confidence.  It  was  their  opinion  that  a  work  which 
should  furnish  a  full  account  of  the  chemical  principles  involved 
in  the  various  organic  changes  originating  in  the  mouth,  and  of 
the  behavior  of  the  metals  and  other  materials  used  in  the 
workroom,  was  very  much  needed  by  their  profession.  Whether 
the  present  work  supplies  this  demand  is  for  the  public  to  deter- 
mine. 

It  is  manifest  that  such  a  book  may  be  constructed  upon  one 
of  two  plans  without  losing  sight  of  the  original  design.  It 
may  be  adapted  either  to  the  wants  of  the  student,  who  desires 
to  get  an  enlarged  view  of  the  profession  upon  which  he  is 
entering,  or  it  may  be  confined  to  those  of  the  practical  work- 
man, who  demands  merely  a  guide  to  those  manipulations  which 
constitute  the  round  of  his  daily  duty. 

In  the  latter  case,  all  that  would  be  required  is  a  brief  state- 
ment of  those  chemical  facts  which  bear  directly  upon  the 
manipulations  alluded  to.  In  the  former,  a  much  more  extensive 
field  is  opened  to  an  author.  He  cannot,  indeed,  neglect  those 
practical  points,  an  acquaintance  with  which  is  so  necessary  to 
the  mechanical  dentist,  but  he  must  not  confine  himself  to  them. 
He  must  show  the  connection  of  this  special  study  with  the  general 
science,  and  point  out  to  the  student  how  it  touches  the  domain 
of  physiological  chemistry  on  the  one  hand,  while,  on  the  other, 


Vm  PREFACE. 

it  demands  an  acquaintance  with  the  truths  of  inorganic  che- 
mistry. 

It  has  been  the  author's  aim,  in  the  following  pages,  to  adapt 
his  work  to  both  classes  of  readers.  He  has  endeavored  to 
make  it  both  a  manual  for  the  practical  man,  and  a  text-book 
for  the  student.  He  has,  therefore,  introduced  a  brief  account 
of  the  general  principles  of  animal  chemistry,  which  must 
necessarily  form  the  basis  of  a  successful  investigation  of  any 
of  its  specialties.  Considering  it  impossible  to  get  a  correct 
idea  of  the  importance  of  the  mouth  and  of  the  processes  which 
take  place  in  it  without  some  knowledge  of  that  great  function 
in  which  it  takes  a  part,  the  author  has  introduced  a  chemical 
history  of  digestion.  In  his  opinion,  this  forms  a  necessary 
preparation  for  the  study  of  the  fluids  of  the  mouth,  of  which 
he  has  given  the  fullest  description  in  his  power. 

In  regard  to  the  practical  details  of  his  work,  the  author 
hopes  he  has  been  sufficiently  precise.  So  much  depends  upon 
the  selection  and  management  of  fuel,  and  so  many  failures 
result  from  ignorance  of  this,  and  of  the  best  modes  of  generat- 
ing and  controlling  high  heats,  that  a  special  chapter  upon  this 
subject  was  deemed  necessary.  In  the  chapter  on  the  different 
metals,  it  is  hoped  that  no  important  practical  suggestion  has 
been  omitted.  The  author  would  call  the  special  attention  of 
practical  mechanical  dentists  to  the  chapters  on  gold,  silver,  and 
copper,  and  particularly  to  the  tables  of  coins  of  the  two  first- 
named  metals,  a  careful  examination  of  which  will  enable  the 
maker  of  plate-work  to  avoid  those  crystalline,  unmalleable 
alloys  that  prove  so  troublesome,  and  to  be  certain  of  the  exact 
composition  of  his  plate,  a  point  the  importance  of  which  it  is 
not  necessary  to  dwell  upon.  The  account  of  the  behavior  of 
the  metals  is  rather  fuller  than  it  would  have  been  had  a  mere 
manual  for  the  practical  man  been  designed ;  but  as  a  text-book 
was  also  aimed  at,  it  was  thought  proper  to  give  as  complete  a 
history  of  the  metals  as  the  plan  of  the  work  would  admit  of. 

The  subject  of  porcelain  has  received  much  attention.  A  full 
account  of  the  materials  used  in  the  manufacture  of  that  beauti- 
ful ware  has  been  introduced,  for  the  benefit  of  those  who  may 
wish  directly  to  collect  them,  and  numerous  formulae  have  been 


PREFACE.  IX 

given  for  the  manufacture  of  teeth.  Those  of  Dr.  A.  A.  Blandy 
can  be  implicitly  relied  upon,  as  thej  have  been  for  some  time 
and  are  still  used  by  him,  with  uniformly  good  practical  results. 

It  has  not  been  thought  necessary  to  encumber  the  margins 
of  the  book  with  citations.  But  few  references  are  given,  and 
these  usually  when  quotations  have  been  made.  The  author 
has  consulted  all  the  authorities  which  were  accessible  to  him. 
He  desires  especially  to  acknowledge  his  obligations  to  the 
recent  admirable  work  of  Lehmann,  the  papers  of  his  trans- 
lator, Dr.  Day,  in  Ranking' s  Half-Yearly  Abstract  and  the 
British  and  Foreign  Medico- Chirurgical  JReviezv,  Dr.  Samuel 
Wright's  articles  on  Saliva,  in  the  London  Lancet,  and  Donald- 
son's and  Porcher's  papers  on  Bernard's  recent  discoveries,  in 
the  American  Journal  of  the  Medical  Sciences,  and  the  Charles- 
ton Medical  Journal  and  Review.  The  treatises  of  Overman 
and  Phillips  on  Metallurgy,  the  Dictionary  of  Ure,  the  Cyclo- 
psedia  of  Chemistry,  by  Booth,  the  w^orks  of  Liebig,  and  the 
various  chemical  journals  have  also  been  freely  used. 

To  Dr.  C.  A.  Harris  the  author  is  indebted  for  many  valuable 
hints,  and  much  important  information  as  to  the  kind  of  che- 
mical knowledge  the  dentist  needs.  To  Dr.  A.  A.  Blandy, 
Professor  of  Operative  Dentistry  in  the  Baltimore  College, 
he  would  also  express  his  acknowledgments,  for  the  practical 
recipes  he  has  furnished  him  with,  and  for  his  kindness  in  allow- 
ing him  to  witness  the  various  manipulations  in  his  operating 
rooms. 


CONTENTS. 


Dedication 

Preface 


PAGE 
V 

vii 


BOOK  I. 

CHAPTER  I. — Ultimate  Chemical  Elements  «f  the  Human  Body  17-22 
Metalloids  .......         19 


Metals    ..... 

CHAPTER  IL — Proximate  Elements  of  the  Bodt 
Mode  of  Combination  in  Organic  Substances 
Compound  Radicals 
Putrefaction 

CHAPTER  III.— The  Albuminous  Group 

Protein  Compounds 
Albumen 
Fibrin  . 
Globulin 
Casein  . 
Gluten  . 
Legumia 
Teroxide  of  Protein 


CHAPTER  IV.- 
Glutin     . 
Chondrin 


-The  Gelatinous  Group 


CHAPTER  V. — Nitrogenous  Basic  Bodies 

Creatine 
Creatinine 
Tyrosine 
Leucine  . 
Sarcosine 
Glycine  . 


20 

22-28 
22 
24 
26 

28-50 
29 
33 
37 
42 
43 
44 
48 

50 
50 
52 

53 
54 

55 
56 
56 

57 

58 


Xll 


CONTENTS. 


Urea 
Xanthine 
Guanine 
Allan  toine 
Cystine  . 
Taurine 


CHAPTER  VI.— Nitrogenous  Acids 
Carbazotic  Acid 
Hippuric  Acid   . 
Uric  Acid 
Inosic  Acid 
Glycocholic  Acid 
TaurochoUc  Acid 


CHAPTER  VII.— Non-Nitrogenous  Acids 
Buli/ric  Acid  Group 

Oxalic  Acid 

Formic  Acid 

Acetic  Acid 

Metacetonic  Acid 

Butyric  Acid 

Valerianic  Acid 

Caproic  Acid 

CEnanthylic  Acid 

Caprylic  Acid    . 
Succinic  Acid  Group 

Succinic  Acid    . 

Sebacic  Acid 
Benzoic  Acid  Group 

Benzoic  Acid 
Lactic  Acid  Group 

Lactic  Acid 
Solid  Fatty  Acids 

jMargaric  Acid  . 

Stearic  Acid 
Oily  Fatty  Acids   . 

Oleic  Acid 
Besinous  Acids 

Lithofellic  Acid 

Cholic  Acid 


CHAPTER  VIII. — Nox-NiTROGENOus  Bases  and  Salts- 
Oside  of  Lipyl  ..... 
Glycerine  ..... 

Salts  of  Oxide  of  Lipyl  or  Fats 


-Haloids 


87 
89 
90 
90 


CONTENTS. 

XIU 

PAGE 

Lipoids  ...... 

95 

Cholesterin         ..... 

95 

Serolin    ...... 

96 

CHAPTER  IX. — Non-Nitrogenous  Neutral  Bodies 

96 

Glucose               ..... 

96 

Milk-Sugar         ..... 

99 

CHAPTER  X.— Pigments      .... 

.       100 

Htematin            ..... 

.      100 

Melanin              ...... 

.       102 

Bile  Pigment      ..... 

.      102 

Urine  Pigment  ...... 

.      103 

BOOK   II. 

DIGESTION. 

CHAPTER  I. — Physiological  Relations  of  Digestion 

CHAPTER  II.— Food  .... 

CHAPTER  III.— Gastric  Digestion 

CHAPTER  IV. — Intestinal  Digestion 

Bile 

Pancreatic  Juice  .... 

Intestinal  Juice  .... 

Contents  of  Intestinal  Canal  and  Excrements 


103 

111 

119 

132 
132 
142 
145 
146 


BOOK  III. 


THE  CHEMISTRY  OF  THE  MOUTH. 

CHAPTER  I.— The  Teeth     .... 

CHAPTER  II.— Saliva  .... 

CHAPTER  III. — On  the  Morbid  Changes  of  Saliva 
Deficient  Saliva 
Redundant  Saliva 
Ptyalism 
Fatty  Saliva 
Sweet  Saliva 
Albuminous  Saliva 
Bilious  Saliva     . 
Bloody  Saliva    . 
Acid  Saliva 


153 

157 

194 
194 

196 
199 
204 
206 
207 
208 
210 
211 


XIV 


CONTENTS. 


Alkaline  Saliva 

Calcareous  Saliva 

Saline  Saliva 

Puriform  Saliva 

Fetid  Saliva 

Acrid  Saliva 

Urinary  Saliva  . 

Gelatinous  Saliva 

Milky  Saliva      , 

Changes  of  the  Saliva  in  Disease 

CHAPTER  IV.— Mucus 

CHAPTER  v.— Salivary  Calculi    . 


PAGE 
214 

215 
215 
216 
216 
217 
218 
219 
220 
220 

222 

231 


BOOK  IV. 

CHEMISTRY  AND  METALLURGY  OF  THE  METALS  AND  EARTHS 
USED  BY  THE  DENTIST. 


PART   I. 

THE  METALS. 

CHAPTER  I. — The  Different  Modes  of  Applying  Heat,  Fur 
NACES,  and  Auxiliary  Apparatus 
The  Blowpipe 
Lamps    . 
Furnaces 
Crucibles 
Cupels    . 
Lutes 
Fuel 
Measurement  of  the  Heat  of  Furnaces 


CHAPTER  II.— Gold 

Metallurgic  Treatment  of  Gold  Ores 

Metallurgy  of  the  Alloys  of  Gold 

Goldbeating 

Alloys  and  Non-Saline  Compounds 

Alloys  of  Gold  . 

Table  of  Coinage  of  Different  Nations 

Salts  of  Gold      . 

CHAPTER  III.— Silver 

Metallurgic  Treatment  of  Silver  Ores 
Amalgamation 
Smelting 


235 
237 
240 
248 
254 
259 
260 
261 
275 

278 
280 
284 
300 
303 
312 
316 
322 

325 
326 
326 
328 


CONTENTS. 

XV 

PAGE 

Metallurgic  Treatment  of  the  Alloys  of  Silver    . 

.      329 

Scorification   ...... 

.      329 

Cupellation    ...... 

.      330 

Liquation        ...... 

.      335 

Crystallization            ..... 

.      335 

Humid  Process           ..... 

.      336 

Silver,  Non-Saline  Compounds,  and  Alloys     . 

.      341 

Alloys  of  Silver             ..... 

.      345 

Table  of  Silver  Coins 

.      347 

Salts  of  Silver — Haloid  Salts    .... 

.      356 

Salts  of  Silver — Oxjsalts          .... 

.      358 

CHAPTER  IV.— Copper 

363 

Metallurgic  Treatment  of  Copper  Ores 

.      365 

Metallurgic  Treatment  of  the  Alloys  of  Copper 

369 

Copper  and  its  Non-Saline  Compounds 

.      371 

Alloys  of  Copper           ..... 

376 

Haloid  Salts       ...... 

379 

Oxysalts — Salts  of  the  Suboxide 

382 

Oxysalts — Salts  of  Black  Oxide 

.      383 

CHAPTER  Y.-ZiNC 

387 

Metallurgic  Treatment  of  Zinc  Ores     . 

.      387 

Zinc  and  Non-Saline  Compounds 

.      388 

Alloys     ....... 

391 

Haloid  Salts       ...... 

391 

Oxysalts             ...... 

392 

CHAPTER  YI.— Tm 

394 

Tin  and  its  Non-Saline  Compounds 

396 

Alloys  of  Tin    . 

400 

Haloid  Salts       ....... 

401 

Oxysalts             ...... 

402 

CHAPTER  YII.— Lead 

403 

Metallurgy  of  Lead       ...... 

403 

Lead  and  its  Non-Saline  Compounds    . 

405 

Alloys  of  Lead  ....... 

407 

Haloid  Salts      ....... 

408 

Oxysalts             ....... 

.  409 

CHAPTER  YIIL— Bismuth 

412 

Bismuth  and  its  Non-Saline  Compounds 

412 

Alloys  of  Bismuth         ...... 

414 

Salts 

415 

XVI 


CONTENTS. 


CHAPTER  IX.— Platinum   . 
Preparation  of  Platinum 
Metallurgy  of  the  Alloys  of  Platinum 
Platinum  and  its  Non-Saline  Compounds 
Alloys    ..... 
Haloid  Salts       .... 
Oxysalts  .... 

CHAPTER  X.— Mercury       . 

Metallurgic  Treatment  of  Mercurial  Ores 
Mercury  and  its  Non-Saline  Compounds 
Amalgams  .... 

Haloid  Salts      .... 
Oxysalts  .... 

Effects  of  Mercury  on  the  System 


PAGE 

416 
418 
422 
424 

428 
429 
437 


CORRUPTIBLE  TEETH. 


PART  II. 

THE  MATERIALS  USED  IN  MAKING  IN 
CHAPTER  I.— Silicon 
CHAPTER  II.— Aluminum     . 
CHAPTER  III.— Potassium  . 
CHAPTER  IV.— Sodium 


CHAPTER  V. — The  Materials  used  for  Porcelain  Teeth 
Clays      .... 
Feldspar 
Quartz  Sand 

CHAPTER  VI.— Porcelain  . 

CHAPTER  VII.— Coloring  Materials 
Oxide  of  Titanium 
Oxide  of  Uranium 
Oxide  of  Manganese 
Oxide  of  Cobalt 

CHAPTER  VIII.— Incorruptible  Teeth 
History  .... 
Preparation  of  Materials 


DENTAL    CHEMISTRY. 


BOOK    I. 

GENERAL  PRINCIPLES  OF  ANIMAL  CHEMISTRY, 


CHAPTER    I. 

THE  ULTIMATE  CHEMICAL  ELEMENTS  OF  THE  HUMAN  BODY. 

In  treating  of  any  subject  connected  -with  animal  life,  it  is 
exceedingly  difficult  to  decide  on  our  point  of  departure.  All 
the  functions  of  a  living  creature  are  so  dependent  one  upon  an- 
other, and  touch  each  other  in  so  many  points,  that  it  is  impos- 
sible to  isolate  one  from  all  the  rest,  and  to  treat  it  as  a  simple 
scientific  unit.  When  we  are  reviewing  the  entire  history  of  the 
living  body,  this  difficulty  is  not  so  sensibly  felt,  for  we  may 
begin  where  we  please,  and  we  are  sure  to  return  to  our  start- 
ing-point if  we  do  but  follow  the  order  of  succession  of  the  dif- 
ferent functions,  so  true  it  is  that  the  vital  actions  move  in  a 
circle.  In  studying  a  special  department  of  physiological  che- 
mistry, however,  Ave  are  immediately  made  to  feel  the  necessity 
of  a  careful  selection  of  our  course,  through  the  abundant  mate- 
rials which  lie  around  us.  A  segregation  of  our  subject  would 
present  an  imperfect  and  limited,  and  therefore  an  untrue  view 
of  it,  while  an  examination  of  all  its  connections  with  the  gene- 
ral life  of  the  body,  however  desirable  to  the  student  who  has 
abundant  leisure  to  devote  to  it,  would,  by  the  extreme  and 
unnecessary  expansion  to  Avhich  it  would  lead,  deter  many  from 

9 


18  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

a  very  Important  and  necessary  study.  In  an  elementary  work 
like  the  present,  designed  especially  for  students,  it  is  incum- 
bent upon  the  author  to  keep  these  facts  in  view,  and  carefully 
to  avoid  running  into  either  of  these  objectionable  extremes. 
We  must  examine,  as  minutely  as  time  will  permit,  the  imme- 
diate relations  of  the  subject  under  consideration,  and  confine 
ourselves  as  closely  as  possible  to  them. 

It  is  proposed  in  the  following  pages  to  consider  the  physio- 
logical chemistry  of  the  natural  organs  of  mastication,  and  to 
examine  the  chemical  principles  upon  which  the  success  or  fail- 
ure of  the  artificial  substances  used  by  the  dentist  to  remedy 
defects  in  these  organs  will  depend.  This,  of  course,  includes 
the  study  of  the  chemical  composition  of  the  teeth,  as  well  as  of 
the  soft  parts  which  surround  them,  and  the  secretions  which 
flow  over  them.  "When  we  consider,  however,  that  this  appa- 
ratus, beautiful  and  perfect  as  it  is,  is  but  subsidiary  to  another 
of  the  utmost  importance  to  the  well-being  of  the  system,  we 
see  the  impropriety  of  limiting  our  view  to  the  mere  mouth. 
Since  the  health  of  the  mouth  is  essential  to  the  perfect  health 
of  the  stomach,  and  since  diseased  conditions  of  the  latter  cavity 
react  upon  the  former,  it  becomes  us  to  understand  the  function 
of  the  one  if  we  would  fully  comprehend  that  of  the  other. 
Moreover,  as  these  combined  functions  form  but  a  part  of  a 
great  organic  process,  it  is  necessary  to  acquire  a  general  notion 
of  the  whole  before  we  can  accurately  determine  the  importance 
of  the  part  we  are  studying.  The  following  pages  will,  there- 
fore, comprise  a  general  account  of  the  process  of  assimilation, 
with  a  more  particular  description  of  the  functions  of  digestion, 
especially  those  preliminary  parts  of  it  which  are  performed  in 
the  mouth,  and  the  changes,  so  far  as  known,  which  these  last 
undergo  in  disease.  The  elementary  nature  of  this  work,  how- 
ever, renders  it  desirable  that  some  general  remarks  on  the  con- 
stituents of  the  human  body  should  be  prefixed. 

The  human  body,  made  up,  as  it  is,  of  a  great  variety  of  tis- 
sues arranged  in  an  harmonious  whole,  is  nevertheless  capable  of 
being  resolved  into  a  number  oi  proximate  elements,  which  form 
the  basis  of  all  the  tissues  and  secretions  of  the  system.  These 
proximate  elements  are  not,  in  the  chemist's  sense  of  the  term. 


CHEMICAL  ELEMENTS  OF  THE  HUMAN  BODY.  19 

simple ;  but  are  each  of  tliem  made  up  of  several  chemical  ele- 
ments. Of  the  latter  substances,  oxygen^  hydrogen,  nitrogen,  and 
carbon  are  found  in  by  far  the  greatest  abundance.  These,  in 
varying  proportions,  form  the  basis  of  all  the  organic  tissues  and 
secretions.  Their  combinations  being  very  complex  will  form 
the  subject  of  a  future  chapter.  There  are  superadded  to  them 
many  other  elements,  which  shall  now  be  very  briefly  enume- 
rated. 

Sulphur  forms  a  part  of  almost  all  the  tissues,  and  composes 
a  very  considerable  proportion  of  some  of  them.  In  its  ele- 
mental form  it  enters  into  the  composition  of  the  very  basis  of 
the  body,  in  albumen  and  fibrin,  and  into  all  the  tissues  com- 
pounded of  these.  It  can  also  be  detected  in  many  of  the  secre- 
tions, especially  in  bile,  of  one  of  the  component  parts  of  which, 
taurine,  it  constitutes  twenty-five  per  cent.  In  combination 
with  other  metalloids  and  metallic  oxides,  it  exists  in  less  abund- 
ance, and  is  less  widely  diffused.  Thus,  we  have  sulphates  in 
the  urine  and  sweat,  and  sulphocyanide  of  potassium  has  been 
said  to  exist  in  appreciable  quantity  in  the  saliva. 

Phosphorus  is  also  very  generally  distributed  through  the 
system.  Like  sulphur,  in  its  elemental  foi'm,  it  constitutes  an 
essential  part  of  the  albumen  and  fibrin.  It  is  found,  in  very 
large  quantity,  in  the  brain  and  nervous  system  as  cerebric  and 
oleophosphoric  acids,  and  entering  also  into  the  composition  of 
several  distinct  cerebral  fats.  It  exists  also  very  abundantly  as 
phosphoric  acid,  in  which  form  it  can  be  extracted  from  the 
blood,  the  bones,  the  muscles,  and  the  urine.  None  of  the  tis- 
sues and  very  few  of  the  secretions  are  destitute  of  this  element. 

Chlorine,  too,  is  very  abundant  in  the  animal  economy ;  not, 
however,  in  its  elemental  form.  It  is  found  in  combination  with 
hydrogen,  as  hydrochloric  acid  in  the  gastric  juice,  and  with 
sodium  and  potassium  in  almost  all  the  fluids  and  in  many  of 
the  solids. 

Silicon,  in  the  form  of  silicic  acid  or  silex,  'is  a  constituent  of 
the  enamel  of  the  teeth,  the  hair,  the  saliva,  the  urine,  the 
blood,  &c. 

Fluorine  was  first  detected  by  Berzelius  in  bones,  teeth, 
and  urine.     His  experiments  were  much  contested,  but  after  a 


20  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

full  discussion  and  numerous  analyses,  the  question  has  been 
finally  settled  in  favor  of  the  views  of  the  great  Swedish  chemist. 

OF  THE  METALS. 

Potassium  is  found  in  the  blood  and  all  the  fluids  as  a  chlo- 
ride. Sulphate  of  potassa,  as  well  as  of  soda,-  exists  in  the 
blood,  urine,  milk,  and  sweat.  In  some  of  the  fluids  the  sul- 
phates are  not  naturally  present,  but  are  formed  during  the 
chemical  process  of  ignition.  The  blood,  lymph,  chyle,  bile, 
milk,  and  urine,  as  well  as  the  juice  of  flesh,  contain  the  phos- 
phates both  of  potassa  and  soda.  In  the  latter  fluid  and  in  milk, 
the  potash  salts  predominate  over  those  of  soda,  while  the  con- 
trary is  true  of  the  other  liquids  named  above. 

Sodium  abounds  as  a  chloride.  As  a  sulphate  and  phosphate 
soda  is  found  in  company  with  potassa.  As  a  phosphate  it  is 
very  generally  difi'used.  The  alkaline  reaction  of  many  of  the 
fluids  is  due  to  the  presence  of  the  tribasic  phosphate  of  soda, 
composed  according  to  the  formula  HO,  2]SraO,  POj+^^HO. 
According  to  Enderlin,  the  phosphate  oftenest  met  with  may  be 
stated  as  3NaO,  PO^.  Phosphate  of  soda  and  ammonia,  the 
mici'oeosmic  salt  of  the  older  chemists  and  of  the  modern  blowpipe 
manipulators,  is  formed  in  large  quantity  in  putrefying  animal 
fluids.     Its  formula  is  IIO,  NH,0,  NaO,  PO^-fSHO. 

Calcium  is  found  more  largely  than  any  other  metal  in  the 
body.  Its  chloride  is  a  constituent  of  the  gastric  juice  and  of 
the  saliva,  and  its  fluoride  of  the  tissues  and  fluids  mentioned 
above  under  the  head  of  fluorine.  As  an  oxide  (lime)  com- 
bined with  acids,  it  is  more  abundant  than  in  any  other  form. 
Phosphate  of  lime  is  a  component  part  of  lymph,  chyle,  blood, 
milk,  urine,  feces,  &c.  Its  principal  seat,  however,  is  in  the 
bones  and  teeth.  There  it  exists  in  the  form  of  bone-earth,  as 
it  is  commonly  termed,  consisting  of  48.45  per  cent,  of  acid  and 
51.55  of  base.  Its  empirical  formula,  consequently,  is  8CaO-f- 
3P0j;  but  it  has  been  thought  to  consist  of  two  tribasic  phos- 
phates, and  therefore  to  be  2CaO,  HO,  PO„4-2  (3CaO,  PO^). 
In  the  urine,  it  is  a  superphosphate.  Carbonate  of  lime  oc- 
curs in  the  bones,  teeth,  &c.,  and  in  morbid  concretions,  as  the 


CHEMICAL  ELEMENTS  OF  THE  HUMAN  BODY.  21 

calcareous  masses  "\vliicli  block  up  tlie  old  cavities  and  bronchial 
glands  of  consumptive  patients. 

Magnesium  is  also  a  component  of  the  human  frame,  and  is 
very  generally  distributed,  though  not  in  such  large  proportion 
as  the  last-named  metal.  Carbonate  of  magnesia  was  supposed 
by  Berzelius  to  be  the  form  in  which  this  earth  exists  in  bone, 
the  phosphate  being  formed  in  the  process  of  analysis,  magne- 
sia having,  as  every  chemist  knows,  a  much  stronger  affinity  for 
phosphoric  acid  than  lime  or  any  of  the  ordinary  bases.  This 
salt  also  forms  a  part  of  the  alvine  dejections  and  other  excre- 
tions'. The  phosphate  is,  as  might  be  expected,  found  in  the  urine, 
and  it  is  in  the  form  of  this  salt  that  magnesia  is  obtained  from 
the  bones.  The  ammoniaeo-magnesian  phosphate  is  tribasic, 
with  twelve  atoms  of  water,  ten  of  which  may  be  expelled  with- 
out loss  of  ammonia.  Its  formula  is,  therefore,  NH^O,  2iMgO, 
POj+2HO+10HO.  It  is  obtained  from  diseased  urine,  uri- 
nary calculi,  and  the  feces  of  patients  laboring  under  typhus 
fever. 

Alumina  is  found  in  the  teeth,  and  was  said  by  Orfila  to 
exist  in  the  bones.  Lehmann  denies  its  presence  in  the  animal 
economy. 

Iron  is  a  constituent  of  hasmatin,  the  coloring  matter  of  the 
blood,  of  lymph,  chyle,  muscles,  bones,  and  many  other  tissues. 
Its  chloride  forms  a  part  of  the  gastric  juice.  Its  phosphate  is 
supposed  to  exist  in  the  hair,  the  pigment-cells,  and  some  of  the 
fluids. 

3Ianganese  is  contained  in  the  hair,  a  fact  which  can  be 
easily  demonstrated  by  fusing  the  ash  of  hair  with  carbonate  of 
soda,  when  the  characteristic  green  tint  of  manganate  of  soda 
will  be  observed.  It  has  also  been  detected  in  bile  and  in  gall- 
stones, and  it  has  been  asserted  that  this  metal  has  been  obtained 
from  healthy  blood. 

Copper  is  reckoned  by  Devergie,  Orfila,  Heller,  and  others  as 
a  normal  constituent  of  the  soft  parts  of  the  blood.  There  is  no 
doubt  of  its  existence  in  gall-stones,  and  it  has  been  fully  proved 
to  be  a  component  part  of  bile. 

Lead  has  also  been  detected  in  the  body,  and  at  one  time 
Orfila  aflSrmed  that  arsenic  was  an  element  of  healthy  human 


22  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

bone.  An  amusing  example  of  the  earnestness  of  his  faith  in 
this  doctrine  took  place  on  the  trial  of  the  celebrated  Madame 
Laffarge.  On  that  occasion  Orfila  was  cited  as  a  witness  for 
the  defendant.  The  case  hinged  upon  the  question  whether  the 
arsenic  which  was  detected  about  the  body,  coffin,  and  earth  of 
the  grave  had  been  derived  from  poison  introduced  into  the  sto- 
mach of  M.  Laifarge.  Orfila  contended  that  it  had  not,  and  in 
reply  to  some  chemical  testimony  adduced  by  the  prosecution, 
in  a  sudden  burst  of  indignation,  he  exclaimed:  "Why,  Mr. 
President,  I  can  take  you  oif  your  seat,  boil  you,  and  obtain 
sufficient  arsenic  from  you  to  exhibit  to  this  jury!"  lie  has, 
however,  since  abandoned  that  idea. 


CHAPTER    II. 

THE  PROXIMATE  ELEMENTS  OF  THE  BODY. 

The  organic  constituents  of  the  human  body,  whether  solids 
or  fluids,  are,  as  already  stated,  formed  from  two  or  more  of  the 
metalloids,  oxygen,  carbon,  nitrogen,  and  hydrogen,  with  or 
without  the  addition  of  sulphur  and  phosphorus. 

There  are  certain  peculiarities  about  the  union  of  these  ele- 
ments in  vital  chemistry  which  demand  notice  in  an  elementary 
work  like  the  present.  One  of  these  peculiarities  has  been 
rather  broadly  stated.  It  has  been  said  that  in  inorganic  bodies 
the  common  combination  is  binary,  while  in  organic  compounds 
it  is  ternary  or  quaternary ;  that  is  to  say,  these  elements  unite 
in  the  one  case  in  twos,  in  the  other  in  threes  or  fours.  A  little 
consideration,  however,  will  show  that  this  is  not  absolutely  true. 
Thus,  ethyl,  which  is  an  organic  radical,  is  binary,  being  a  carbo- 
hydrogen,  while  chromic  alum,  a  purely  inorganic  compound,  is 
ternary,  being  made  up  of  sulphuric  acid,  oxide  of  chromium, 
and  alumina. 

It  is  true,  however,  that  the  mode  of  combination  in  the  inor- 
ganic is  much  more  simple  than  in  the  organic  world.    We  may 


PROXIMATE  ELEMENTS  OF  THE  BODY.  23 

illustrate  this  by  the  commonly  quoted  case  of  carbonate  of 
ammonia.  To  express  this  by  chemical  notation,  we  may 
arrange  the  elements  as  (COjNIIJ'^  without  giving  any  idea  of 
the  mode  of  union,  but  simply  expressing  the  atomic  constitu- 
tion of  the  compound.  But  upon  examination,  we  detect  a 
definite  arrangement  of  these  elements.  If  we  boil  this  sub- 
stance with  a  paste  made  of  recently  slaked  lime,  in  a  vessel 
communicating  with  water,  we  shall  find  the  liquid  in  the 
receiver  becoming  gradually  charged  with  the  volatile  alkali 
(NH^O),  ammonia,  while  a  white  powder  subsides  in  the  retort. 
If  we  now  direct  our  attention  to  this  precipitate,  we  shall  find 
that  it  efi'ervesces  with  acids,  giving  off  a  gas  which  colors  lit- 
mus paper  red,  and  which,  by  the  application  of  the  proper 
tests,  is  ascertained  to  be  carbonic  acid  (COJ.  Now,  if  we  con- 
nect again  the  different  pieces  of  the  apparatus,  so  that  the 
acid  gas  shall  pass  through  the  alkaline  solution,  we  reproduce 
the  identical  substance  first  experimented  on.  This  completes 
the  proof  that  the  compound  consists  of  carbonic  acid  and  ammo- 
nia directly  combined.  The  formula,  therefore,  will  be  NH^O, 
CO2,  and  this  is  a  type  of  the  binary  method  of  combination,  so 
common  in  inorganic  nature. 

An  organic  substance  submitted  to  the  same  operations  yields 
a  totally  different  result.  If  to  a  concentrated  solution  of  urea 
nitric  acid  be  added,  a  sudden  crystallization  reduces  nearly  the 
whole  solution  to  a  mass  of  fine  leaves  or  scales.  Nothing  escapes 
as  in  the  previous  example,  and  we  have  to  examine  the  liquid 
and  the  crystalline  product  to  ascertain  what  changes  have 
taken  place.  In  the  former,  we  find  nothing  but  the  excess  of 
urea  or  of  nitric  acid,  as  the  case  may  be.  In  the  latter,  we 
detect  precisely  the  same  substance  as  before,  with  the  addition 
of  nitric  acid.  If  we  add  to  the  nitrate  of  urea,  thus  obtained, 
oxalic  acid  in  solution,  we  shall  find  the  nitric  acid  gradually 

*  In  stating  this  example  of  inorganic  combination,  no  distinction  has 
been  made  between  the  gaseous  ammonia,  NII3,  and  the  oxide  of  ammo- 
nium, NH4O,  which  forms  the  basis  of  ammoniacal  salts ;  because  the  full 
account  of  these  complicated  reactions  would  have  only  obscured  the  sub- 
ject, and  diverted  the  mind  of  the  reader  from  the  main  point,  viz. :  the 
illustration  of  the  method  of  combination  in  inorganic  nature. 


24  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

appearing  in  the  solution,  and  the  oxalic  acid  taking  its  place  in 
the  salt.  Now,  this  process  is  diametrically  opposite  to  the 
former.  Urea  is  found  to  behave  precisely  as  lime  or  any  other 
metallic  oxide  would  do,  constituting  what  chemists  call  a  sali- 
fiable base,  that  is,  a  substance  capable  of  being  converted  into 
a  salt  by  the  addition  of  an  acid  or  a  metalloid  halogen.  If, 
however,  we  subject  urea  to  the  action  of  heat,  we  decompose 
it,  and  by  a  series  of  processes,  resolve  it  into  its  original  ele- 
ments, and  no  binary  combinations  take  place  except  those 
which  are  manifestly  the  result  of  decomposition  and  recomposi- 
tion  in  the  changing  substance.  Manifestly,  the  elements  in 
this  compound,  are  united  in  a  manner  entirely  diiferent  from 
that  in  which  they  exist  in  the  example  cited  from  the  inorganic 
world.  Our  notation  must  also  differ.  We  express  the  entire 
compound  in  a  single  unbroken  formula,  CjNgH^Oj. 

There  is  another  difference  between  organic  and  inorganic 
compounds,  which  is  always  taken  into  consideration  when  esti- 
mating the  difference  between  these  two  classes  of  bodies.  In 
inorganic  nature,  the  elements  are  usually  united  in  a  small  num- 
ber of  atoms.  Thus,  water  contains  only  one  atom  of  hydrogen 
and  one  of  oxygen ;  carbonic  acid,  one  of  carbon  and  two  of 
oxygen;  muriatic  acid,  one  of  hydrogen  and  one  of  chlorine. 
Organic  compounds,  on  the  contrary,  are  far  more  complex  in 
their  composition.  Creatine,  for  example,  the  crystalline  ele- 
ment of  watery  extract  of  flesh,  contains,  according  to  Liebig, 
eight  parts  of  carbon,  three  of  nitrogen,  eleven  of  hydrogen, 
and  six  of  oxygen  (CgN3HjjOg),  and  the  formula  for  protein 
(C40H30N3OJ2)  is  still  more  complex. 

The  peculiarity  which  these  compounds  possess  of  acting 
towards  alkalies  and  acids  like  the  common  bases  is  one  of  the 
most  remarkable  facts  in  organic  chemistry.  The  theory  of 
their  combination  is  known  as  the  doctrine  of  compound  radi- 
cals. It  is  one  of  the  recent  and  most  striking  developments  of 
this  doctrine  that  one  substance  may  be  substituted  for  an- 
other, in  these  remarkable  bodies,  without  materially  changing 
the  relations  of  the  compound  to  other  reagents.  Hoffman's 
brilliant  discoveries  have  disclosed  the  fact  that  organic  com- 
pound radicals  may  be  substituted  for  the  hydrogen  of  ammo- 


PROXIMATE  ELEMENTS  OF  THE  BODY;  25 

nia,  and  yet  the  new  substance  retain  many  of  tlie  marked  pro- 
perties of  the  original  compound.  Thus,  three  atoms  of  ethyl, 
which  is  the  organic  base  of  ether,  may  take  the  place  of  the 
three  atoms  of  hydrogen,  so  that  the  formula  would  be  N(C4H5)3 
instead  of  NH..  So  we  may  have  a  tetrethylammonium  or 
N(C4H3)^  instead  of  NH^;  and  even  more  than  this,  several 
organic  radicals  may  be  present  in  a  new  compound,  each  one 
intruding  itself  in  the  place  of  one  of  the  atoms  of  hydrogen, 
and  yet  the  general  features  of  ammonia  and  ammonium  be  still 
recognizable. 

By  an  examination  of  these  facts,  we  can  easily  discover  the 
reasons  of  the  remarkable  instability  of  organic  compounds.  It 
is  well  known  that  the  larger  the  number  of  atoms  which  enter 
into  the  constitution  of  a  body,  the  greater  is  its  j^roneness  to 
decomposition.  Thus,  protoxide  of  chromium,  which  contains 
one  atom  of  oxygen,  can  be  deprived  of  its  oxygen  only  by  car- 
bon and  the  strong  heat  of  a  blast  furnace ;  while  chromic  acid, 
which  contains  three  atoms  of  the  metalloid,  is  reduced  to  a 
protoxide  by  the  mere  presence  of  alcohol  and  a  free  acid  at 
the  common  temperature  of  the  atmosphere,  or  when  isolated, 
by  simple  contact  with  any  organic  body.  Besides,  the  organic 
compounds  of  the  human  body  usually  contain  nitrogen,  and 
that  not  in  the  form  of  nitric  acid  or  ammonium,  which  are  its 
most  stable  combinations,  and,  consequently,  those  to  which  it 
tends.  This  we  know  is  the  most  unfixed  element  in  nature. 
Held  to  other  bodies  by  a  weak  affinity,  gaseous  in  its  form,  it 
is  easily  disengaged  from  its  combinations.  Chloride  of  nitro- 
gen, the  most  terribly  explosive  substance  known,  is  an  example 
of  this  powerful  tendency  to  almost  spontaneous  decomposition. 
The  slightest  jarring  of  this  oily  compound  produces  a  tremen- 
dous explosion.  This  disposition  is  very  much  increased  in  or- 
ganic bodies  by  the  presence  of  the  elements  of  water,  which 
furnish  precisely  those  conditions  most  favorable  to  change  in 
the  relations  of  this  metalloid. 

This  extreme  mobility  of  atoms  is  essentially  necessary  to 
these  substances,  because  they  require  countless  modifications 
to  meet  the  ever-varying  necessities  of  the  system,  and  these 
modifications  must  be  impressed  upon  them  by  feeble,  delicate, 
but  constant  chemical  agencies. 


26  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

The  progress  of  putrefaction  very  well  illustrates  this  extreme 
mobility  of  particles.  In  order  that  this  process  should  begin 
and  continue,  nothing  more  is  necessary  than  that  atmospheric 
air,  a  due  degree  of  heat,  and  organic  matter,  itself  in  a  state 
of  change,  should  be  present.  It  is  well  known  that  the  act  of 
fermentation  has  been  for  a  long  time  the  subject  of  a  warm 
dispute  between  the  disciples  of  Liebig  and  the  microscopists. 

The  discovery  of  the  yeast-plant,  and  the  apparently  direct 
influence  of  the  growth  of  that  infusorial  vegetable  upon  the  pro- 
cess of  fermentation,  led  to  the  hypothesis  that  all  these  changes 
depended  upon  the  growth  of  microscopic  beings  in  the  fer- 
menting or  putrefying  fluids,  and  that  their  results  were  no- 
thing but  the  secretions  and  excretions  of  these  minute  "organ- 
isms. 

The  experiments  of  Helmholtz,  however,  seem  decisive  upon 
this  point.  This  observer  found  that,  when  animal  matter  was 
boiled,  and  subjected  to  the  action  of  air  which  had  passed 
through  a  redhot  tube,  no  change  took  place,  though  the  sub- 
stances experimented  on  were  subjected  to  the  influence  of 
oxygen  for  eight  weeks  in  the  heat  of  summer.  As  soon,  how- 
ever, as  these  same  fluids  were  exposed  to  the  open  air,  putre- 
faction took  place,  and  multitudes  of  infusoria  were  found  in 
the  decomposing  liquids.  This  would  seem  to  favor  the  micro- 
scopic theory,  but  our  inquirer  did  not  stop  here.  He  subjected 
the  same  substances  to  the  action  of  oxygen  produced  by  the 
decomposition  of  water  by  the  electric  current,  and  still  no 
change  took  place.  It  is,  therefore,  manifest  that  putrefaction 
in  the  open  air  must  depend  upon  some  constituent  of  the  atmo- 
sphere which  is  destroyed  or  modified  by  a  red  heat.  Now,  infu- 
sorial germs  of  living  creatures  and  putrescent  exhalations  from 
dead  organic  matter  were  considered  by  him  to  be  the  only  sub- 
stances to  be  found  in  this  class.  To  determine  which  of  these 
formed  the  exciting  cause  of  putrefaction,  he  resorted  to  an- 
other series  of  experiments.  He  took  the  same  substances  as 
before,  and  introduced  into  them  other  putrefiable  fluids  which 
had  not  been  excluded  from  the  air.  This  he  did  through  the 
pores  of  a  bladder  which  the  smallest  infusorial  germs  could  not 
penetrate.     Under  these  circumstances,  he  found  that  putrefac- 


PROXIMATE  ELEMENTS  OF  THE  BODY.  27 

tion  went  on  "with  as  great  rapidity  as  when  the  fluids  "were 
directly  exposed  to  the  action  of  the  atmosphere,  with  this  dif- 
ference, however,  that  they  remained  clear,  and  contained  no 
infusoria.  He  therefore  concluded  that  this  great  chemical 
change  can  be  effected  in  a  substance,  simply  by  the  presence  of 
another  undergoing  decomposition,  the  motion  already  existing 
among  the  particles  of  the  latter  producing  the  same  molecular 
change  among  those  of  the  former,  and  predisposing  it  to  the 
absorption  and  assimilation  of  oxygen,  by  means  of  which  the 
new  products  of  these  changes  are  formed.  The  discovery  of 
pyrrldne  and  the  investigation  of  its  properties  give  additional 
probability  to  the  results  of  Helmholtz.  Of  Liebig's  reply  to 
his  theory  of  fermentation,  we  have  nothing  to  say  at  present, 
as  it  does  not  concern  the  question  we  are  discussing. 

The  tendency  of  all  these  decompositions  and  recompositions 
is  to  the  production  of  compounds  of  greater  stability.  Thus, 
we  always  find  carbonic  acid,  ammonia  and  its  carbonate,  result- 
ing from  the  decomposition  of  animal  bodies;  and  usually  sul- 
phuretted, carburetted,  and  phosphuretted  hydrogen,  together 
with  cyanogen  and  hydrocyanic  acid.  The  presence  of  these  lat- 
ter substances  has,  however,  been  denied  by  Mr.  Walter  Lewis, 
of  London,  on  the  strength  of  certain  experiments  and  analyses 
made  by  him  in  vaults  and  catacombs.  He  could  detect  no- 
thing in  the  air  of  the  coffins  which  he  examined  except  nitro- 
gen, ammonia,  carbonic  acid,  common  air,  and  animal  matter  in 
suspension.  The  corrosions  of  the  lead  coffins  were  always 
found  to  have  been  accomplished  by  carbonic  acid,  no  traces  of 
either  sulphuric  acid  or  sulphuretted  hydrogen  being  found  in 
them. 

If,  now,  we  proceed  to  inquire  how  these  elements  are  put 
together  in  the  animal  economy,  we  shall,  at  first  sight,  be 
struck  with  the  very  marked  difference  between  the  tissues 
themselves  and  the  secretions.  Formed,  as  they  are,  from  the 
same  common  mass  of  blood,  we  find,  nevertheless,  that  the  tis- 
sues invariably  contain  nitrogen,  while  the  secretions  are  often 
deficient  in  this  ingredient.  This  has  led  to  a  general  division 
of  the  substances,  composing  the  body,  into  two  great  classes,  the 
azotized  and  no7i-azotized  compounds.    The  former  class  is  again 


28  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

subdivided  into  excreted  and  Mstogenetic  substances,  and  these 
last  into  the  albuminous  and  gelatinous  groups.  The  first  of 
these  groups  is  characterized  by  very  decided  peculiarities,  to 
which  we  shall  now  briefly  advert. 


CHAPTER    III. 

THE  ALBUMINOUS  GROUP. 

One  of  the  great  steps  which  animal  chemistry  has  made,  is 
the  discovery  of  the  identity  of  the  forms  of  this  group  in  the 
two  great  divisions  of  the  organic  world.  The  freshly  expressed 
juice  of  vegetables  allowed  to  stand  becomes  turbid,  and  a  sepa- 
ration of  its  constituents  takes  place.  A  green  gelatinous  pre- 
cipitate falls,  which,  after  the  removal  of  the  coloring  matter, 
remains  as  a  grayish  mass.  This  spontaneous  coagulation,  so 
closely  resembling  that  which  occurs  in  blood,  has  caused  the 
name  vegetable  fibrin  to  be  applied  to  the  substance  under  con- 
sideration. 

The  green  parts  of  vegetables  being  crushed  aff"ord  a  juice 
which  is  not  clarified  by  filtration,  and  not  readily  by  the  pro- 
cess above  described.  The  fluid  remaining  after  the  coagula- 
tion of  the  fibrin  may  be  subjected  to  the  temperature  of  140° 
or  160°,  when  it  will  coagulate  in  the  same  manner  as  serum  or 
white  of  egg.  This,  purified  by  the  removal,  by  ether,  of  the 
green  fatty  matter  which  is  entangled  in  its  meshes,  is  vegetable 
albumen. 

"When  peas,  beans,  or  lentils  are  softened  in  cold  water,  fhen 
ground  with  that  fluid,  and  the  mass  farther  diluted  and  strained 
through  a  fine  sieve,  there  passes  through  a  solution  of  casein, 
which  is  always  like  milk,  turbid,  partly  from  suspended  fat, 
partly  from  the  gradual  action  of  the  air  on  the  dissolved  casein, 
lactic  acid  being  slowly  formed,  which  causes  a  gradual  separa- 
tion. This  solution  has  all  the  characters  of  skimmed  milk; 
it  is  coagulated  by  acids,  not  by  heat,  and  forms  a  pellicle  when 


ALBUMINOUS  GROUP.  29 

heated.  It  also  coagulates  after  long  standing,  from  the  forma- 
tion of  lactic  acid;  and,  when  the  coagulum  putrefies,  the  odor 
is  exactly  that  of  putrid  cheese."  This  is,  of  course,  vegetable 
casein. 

"  The  chemical  analysis  of  these  three  substances  has  led  to 
the  very  interesting  result  that  they  contain  the  same  organic 
elements  united  in  the  same  proportion  by  weight ;  and  what  is 
still  more  remarkable,  that  they  are  identical  in  composition  with 
the  chief  constituents  of  blood,  animal  fibrin,  and  albumen. 

"  They  all  three  dissolve  in  concentrated  muriatic  acid  with 
the  same  deep-purple  color,  and  even  in  their  physical  charac- 
ters animal  fibrin  and  albumen  are  in  no  respect  different  from 
vegetable  fibrin  and  albumen.  It  is  especially  to  be  noticed 
that,  by  the  phrase  identity  of  composition,  we  do  not  here 
imply  mere  similarity,  but  that  even  in  regard  to  the  present 
relative  amount  of  sulphur,  phosphorus,  and  phosphate  of  lime, 
no  difference  can  be  observed."* 

PROTEIN  COMPOUNDS. 

These  are  all  called  protein  compounds,  after  Mulder,  who 
claims  to  have  discovered  a  substance  from  which  they  may  all 
be  formed  by  the  addition  of  varying  proportions  of  sulphur  and 
phosphorus.  To  this  he  gave  the  name  protein  (from  Tt^utivi-i, 
I  take  the  first  rank).  This  theory  of  his,  at  first  adopted  and 
afterwards  controverted  by  Liebig,  has  led  to  sharp  and  ani- 
mated discussions  between  him  and  the  adherents  of  the  Giessen 
school.  A  brief  statement  of  the  theory  itself  and  the  disco- 
veries upon  which  it  is  based,  followed  by  an  account  of  Liebig's 
objections,  will  put  the  whole  subject  in  an  intelligible  form. 

Mulder  says  that  such  a  process,  as  is  about  to  be  described, 
will  give  us  protein  in  a  state  of  purity.  Any  one  of  the  albu- 
minous group  of  proximate  elements,  albumen,  fibrin,  or  casein, 
is  to  be  washed  first  with  water  to  separate  soluble  salts  and 
water  extractive,  then  in  alcohol  to  get  rid  of  substances  soluble 
in  that  menstruum,  and  lastly  in  ether  to  dissolve  the  fatty  mat- 

*  Liebig,  Animal  Chemistry. 


30  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

ters  which  are  always  present.  Dilute  liydrocliloric  acid  is  then 
added,  and  the  suhstance  is  digested  in  it  till  the  phosphate  of 
lime  is  all  taken  up.  If  now  it  be  dissolved  in  a  solution  of 
caustic  potash  at  120°  F.,  two  new  substances  make  their  ap- 
pearance in  the  fluid,  sulphuret  of  potassium  and  phosphate  of 
potash.  Acetic  acid  is  now  added  very  carefully  to  exact  satu- 
ration, the  precipitate  thrown  on  a  filter  and  washed  till  the 
rinsings  no  longer  leave  a  residue  upon  evaporation  on  platinum 
foil. 

The  substance  thus  obtained  is,  when  moist,  in  grayish  flocks, 
which  dry  to  an  amber-colored  powder.  It  differs  from  that 
which  was  originally  subjected  to  the  operation.  It  is  insoluble 
in  water,  alcohol,  or  ether,  tasteless  and  inodorous.  It  burns 
when  exposed  to  the  air  without  leaving  any  ash.  If  boiled? 
with  free  exposure  to  atmospheric  air,  it  is  oxidated.  It  is  solu- 
ble in  dilute  acids,  forming  a  compound  with  them  which  is  pre- 
cipitated by  an  excess  of  acid.  Acetic  acid  and  the  tribasic 
variety  of  phosphoric  acid,  however,  form  an  exception  to  this 
rule,  and  dissolve  it  in  all  proportions.  It  is  precipitated  by 
alkalies,  metallic  salts,  ferrocyanide  and  ferridcyanide  of  potas- 
sium, tannin,  and  absolute  alcohol. 

From  these  properties  Mulder  was  led  to  believe  that  he  had 
obtained  a  new  organic  radical  by  the  separation  of  sulphur  and 
phosphorus  from  the  original  albuminous  substance,  and  that 
consequently,  this  group  was  formed  by  the  simple  addition  of 
one  of  these  metalloids  to  this  fundamental  radical.  He  found 
its  composition  to  be 

Oxygen    ......     23.3 

Carbon     ......     55 

Hydrogen  .         .         .         .         .7.2 

Nitrogen  ......     14.5 


100. 


From  this,  he  deduced  the  formula  C^qHjjN^Ojj.  He  has 
subsequently  repeatedly  changed  it.  Another  of  his  formulas 
(proceeding  upon  the  basis  of  the  atomic  weights,  oxygen  100, 
carbon  76.437,  hydrogen  6.24,  nitrogen  88.36)  is  C^oH^^N^^Oj^. 


ALBUMINOUS  GROUP.  31 

His  latest  formula  is  C3gH25N^Ojo  +  2HO.  Liebig's  formula, 
during  the  time  that  he  recognized  Mulder's  discovery,  was 
C,,H3,NgOj,.     The  symbol  is  Pr. 

To  this  theory  of  Mulder,  it  is  objected  first,  that,  as  it  is 
nearly  if  not  quite  impossible  to  obtain  chemically  pure  albu- 
men, fibrin,  or  casein,  so  it  must  be  equally  or  even  more  diflB- 
cult  to  isolate,  with  any  kind  of  precision,  their  base  or  radical. 
Not  one  of  these  bodies  has  ever  been  exhibited  in  a  chemically 
pure  soluble  state,  so  that  any  deductions  as  to  their  ultimate 
composition  must  at  this  time  be  premature. 

Besides,  it  is  urged  that  Mulder  has  not  succeeded  in  doing 
what  he  attempted  to  do;  that  is,  in  effecting  a  total  separation 
of  sulphur  and  phosphorus  from  fibrin  or  albumen.  He  has 
himself  discovered  that,  under  certain  circumstances,  albuminous 
bodies,  though  containing  sulphur,  might  fail  to  give  any  evidence 
of  it,  when  interrogated  by  the  ordinary  reagents.  Protein  is 
in  this  condition.  The  potash  with  which  it  was  boiled  has  ren- 
dered it  impossible  to  appreciate  its  sulphur  by  the  ordinary 
tests ;  but  more  delicate  means  of  research  have  shown  this 
metalloid  to  be  still  present,  and  Mulder  himself  has  detected  it. 

In  reply  to  this  objection,  Mulder  declares  that  the  sulphur  is 
found  as  hyposulphurous  acid,  resulting  from  an  imperfect  de- 
composition of  the  albumen,  fibrin,  or  casein  which  has  been 
employed  in  the  manufacture  of  protein.  He  thinks  the  sul- 
phur in  these  compounds  is  first  united  with  amidogen,  and  then 
combined  with  the  protein  as  sulphamide;  so  that,  when  treated 
with  potash,  two  atoms  of  sulphamide  (NH^S)  combine  with  two 
atoms  of  water,  forming  ammonia,  which  escapes,  and  hyposul- 
phurous acid,  which  combines  with  the  non-sulphurous  atomic 
group  to  form  those  compounds  that  yield  no  sulphur  reaction 
with  silver. 

Lehmann  uses  the  following  language  in  regard  to  this  opi- 
nion of  Mulder: — 

"  It  certainly  is  true  that  all  these  compounds,  on  being 
digested  with  the  fixed  caustic  alkalies,  develop  ammonia,  and 
that  those  yielding  the  sulphur  reaction  contain  more  nitrogen 
than  those  which  do  not  exhibit  it.  The  assumption  of  the 
presence  of  sulphamide  in  these  substances  must,  however,  still 


32  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

be  regarded  as  a  somewhat  hazardous  hypothesis  ;  in  the  first 
place,  because  we  are  as  yet  wholly  unacquainted  with  this  sul- 
phamide,  whether  in  an  isolated  or  combined  state;  secondly, 
because  a  combination  of  hyposulphurous  acid  with  an  organic 
scarcely  basic  substance  is  as  unlocked  for  a  jihenomenon  as 
that  it  should  not  be  separated  by  stronger  acids  from  its  com- 
bination with  the  protein;  and  lastly,  because  the  hyposulphites 
yield  a  most  evident  sulphur  reaction  when  heated  with  organic 
substances  on  silver  foil. 

"  Mulder,  in  like  manner,  assumes  that  the  phosphorus  con- 
tained in  albumen  exists  in  the  state  of  phosphamide,  H^NP, 
a  purely  hypothetical  body,  and  totally  different  from  Gerhard's 
phosphamide,  whose  amide  nature  is,  moreover,  very  doubtful. 
These  are  some  of  the  grounds  on  which  w^e  have  been  led  to 
regard  Mulder's  view  as  a  mere  scientific  fiction." 

This  is  the  present  state  of  the  protein  controversy,  a  discus- 
sion which  has  rallied  the  most  powerful  and  acute  minds  on 
one  side  or  the  other,  and  which  has  been  productive  of  great 
collateral  benefit  to  organic  chemistry,  from  the  stimulus  it  has 
given  to  research,  and  the  new  facts  it  has  elicited.  Mulder 
has  himself  admitted  that  some  of  his  early  generalizations,  as, 
for  example,  the  proportioning  of  protein,  phosphorus,  and  sul- 
phur in  the  difi'erent  histogenetic  substances,  were  too  hasty. 
Whatever  view,  however,  may  be  taken  of  the  possibility  of  iso- 
lating protein,  chemists  are  generally  agreed  in  regarding  the 
hypothesis  as  a  valuable  one  in  the  classification  of  the  proxi- 
mate elements  of  the  body;  and  the  term  23rotein-co7ni3ounds  is 
used  by  the  most  decided  opponents  of  Mulder's  theory. 

These  compounds  possess  some  remarkable  properties  in  com- 
mon. Most  of  them  exist  in  two  modifications,  a  soluble  and 
an  insoluble.  The  soluble  modification,  when  dry,  is  yellowish 
and  translucent,  and  devoid  of  taste  or  smell.  It  is  soluble  in 
water,  but  insoluble  in  alcohol  or  ether,  and  when  once  preci- 
pitated by  alcohol  from  its  solution  in  water,  it  usually  loses  its 
solubility  in  the  latter  menstruum.  The  watery  solution  is  pre- 
cipitated by  the  metallic  salts,  the  acid  of  which  is  commonly 
found  in  the  precipitate.  The  majority  of  them  are  not  preci- 
pitated by  alkalies  or  vegetable  acids,  but  by  mineral  acids, 


ALBUMINOUS  GROUP.  33 

except  the  phosphoric  and  by  tannic  acid.  They  are  converted 
into  the  insoluble  form  by  boiling  or  by  precipitation  with  the 
mineral  acids. 

The  insoluble  compounds  when  dry  are  white,  tasteless,  and 
inodorous ;  insoluble  in  water,  alcohol,  or  ether,  but  soluble  in 
alkalies,  from  which  they  are  precipitated  by  neutralization  with 
acids.  Acetic  and  organic  acids  generally  dissolve  them,  and 
both  ferrocyanide  and  ferridcyanide  of  potassium  precipitate 
them  from  these  solutions.  The  concentrated  acids  do  not  dis- 
solve them,  but  form  with  them  compounds  insoluble  in  acidu- 
lated water,  but  soluble  in  pure  water,  after  first  swelling  and 
becoming  gelatinous  in  appearance.  Concentrated  nitric  acid 
turns  them  yellow;  strong  hydrochloric  acid,  with  free  access  of 
air  and  moderate  warmth,  gives  them  a  fine  blue  color.  Mil- 
Ion's  test,  said  to  be  the  most  delicate,  is  made  by  dissolving 
one  part  of  mercury  in  two  parts  of  nitric  acid  containing  four 
and  a  half  equivalents  of  water.  The  substance  to  be  tested, 
after  having  been  mixed  with  this  fluid,  or  moistened  with  it, 
if  it  be  a  tissue,  is  then  heated  to  between  140°  and  212°,  when 
it  acquires  a  deep-red  tint  not  to  be  dispelled  by  prolonged 
boiling  or  exposure  to  the  air. 

ALBUMEN. 

Among  the  histogenetic  substances  albumen  is  of  the  very  first 
importance.     It  is  undoubtedly  the  origin  of  the  different  tissues. 

Lehmann  and  Soberer  have  shown  that  albumen  varies  very 
much  with  the  source  whence  it  has  been  derived,  owing  to  cer- 
tain adventitious  admixtures.  Thus,  the  albumen  of  the  blood 
differs  from  that  of  the  egg ;  the  albumen  of  a  hen's  egg  from 
that  of  a  dove's ;  and  the  albumen  of  one  man's  blood  from  that  of 
another's;  and  that  of  the  blood  of  the  same  man  even  difi"ers  at 
different  times.  These  variations  are  not  only  confined  to  the 
saturating  capacity  of  these  different  albumens,  but  extend  to 
their  chemical  constitution,  more  especially  their  proportion  of 
sulphur.  Albumen  may  be  studied  in  two  forms,  which  we 
have  just  shown  to  be  common  to  all  protein  compounds,  the 
soluble  and  insoluble  modification. 
8 


34  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

Soluble  albumen,  dried  in  the  air,  is  a  pale-yello"n-isli,  trans- 
lucent mass,  easy  of  pulverization.  The  specific  gravity  of  the 
albumen  of  the  hen's  egg  has  been  ascertained  to  be  1.3144;  or 
after  calculation,  rejecting  the  salts,  1.2617.  It  becomes  posi- 
tively electric  by  friction.  It  is  inodorous,  tasteless,  and  nei- 
ther acid  nor  alkaline  in  its  reaction.  It  swells  in  Avater,  and 
does  not  dissolve  readily  unless  some  alkaline  salt  has  been 
added.  It  is  insoluble  in  alcohol  and  ether.  Dried  in  vacuo, 
or  at  a  temperature  below  122°,  it  can  be  heated  to  212°  with- 
out assuming  the  insoluble  form.  The  aqueous  solution,  how- 
ever, becomes  turbid  at  140°,  coagulates  perfectly  at  145°,  and 
separates  in  flakes  at  167°.  When  excessively  diluted  no  change 
takes  place  below  194°,  and  coagula  will  only  separate  after  long 
boiling. 

Albumen  may  be  precipitated  by  dilute  alcohol.  Strong  alco- 
hol coagulates  it.  Ether  is  said  to  coagulate  the  albumen  of 
eggs,  but  not  that  of  serum.  This  distinction,  however,  is  not 
constant.  The  oils  do  not  affect  it.  Creasote  and  anilin  coagu- 
late it.  Most  acids  render  it  insoluble;  but,  except  tribasic 
phosphoric  acid,  do  not  precipitate  it,  unless  added  in  excess. 
Tannic  acid  is  the  only  organic  acid  which  precipitates  it.  It 
is  thrown  down  by  metallic  salts,  but  not  by  alkalies. 

Albumen  is  rarely  found  isolated  in  the  economy,  being  usu- 
ally in  combination  with  some  alkali.  Lehmann  found  that  in 
the  albumen  of  hens'  eggs,  1.58  of  soda  was  united  with  100  of 
albumen.  This  has  a  slightly  alkaline  reaction,  is  more  soluble 
than  pure  albumen,  and  coagulates  in  a  white  gelatinous  mass 
instead  of  subsiding  in  flakes.  The  alkaline  reaction  is  stronger 
after  boiling  than  before,  showing  that  a  portion  of  alkali  must 
have  been  liberated  during  the  process  of  coagulation.  The  free 
alkali  combines  with  a  small  portion  of  the  albumen  to  form 
albuminate  of  soda,  which  remains  in  solution.  The  albuminate 
of  soda,  when  saturated  with  acetic  acid,  on  the  application  of 
heat,  coagulates  in  flakes  which  can  be  collected,  while  the  ordi- 
nary precipitated  albumen  of  the  egg  passes  through  the  filter 
and  soon  clogs  its  pores. 

When  this  albuminate  of  soda  is  treated  with  dilute  alcohol,  a 


ALBUMINOUS  GROUP.  35 

portion  is  precipitated,  free  from  alkali  and  poor  in  salts,  while 
there  remains  in  solution  the  true  albuminate  of  soda.  A  far- 
ther addition  of  alkali  to  normal  albumen  changes  its  proper- 
ties, so  that,  on  the  application  of  heat,  there  is  formed  a  trans- 
lucent jelly,  containing,  according  to  Lehmann,  4.69  parts  of 
potash,  or  3.14  of  soda  to  100  parts  of  albumen  free  from  salts. 
On  diluting  this  solution  with  water,  it  no  longer  yields  any  pre- 
cipitate on  the  application  of  heat.  Yv'hen  treated  with  excess 
of  alkali,  it  can  be  precipitated  by  any  of  the  acids  which  do 
not  ordinarily  throw  down  albumen  from  its  solutions.  When 
its  solution  is  boiled,  numerous  vesicles  are  formed  which  adhere 
closely  to  the  bottom  of  the  vessel;  and,  on  evaporation  in  the 
air,  it  becomes  covered  with  a  transparent  film  of  coagulated 
albumen,  so  tliat  it  has  occasionally  been  mistaken  for  casein. 
It  yields  a  perfect  flaky  coagulum  on  boiling,  after  the  addition 
of  an  alkaline  salt,  either  dry  or  in  the  saturated  solution. 

Acids  and  metallic  salts  have  nearly  the  same  reactions  with 
this  variety  as  with  the  common  albumen.  Organic  acids,  added 
in  excess,  cause  the  albumen  to  remain  dissolved  on  boiling ;  but 
the  addition  of  a  salt,  such  as  sulphate  of  soda,  chloride  of 
sodium  or  of  ammonium,  causes  a  flaky  precipitate.  These  acid 
solutions  also  become  covered  with  a  casein-like  film  on  evapo- 
ration. 

Coagulated  albumen  possesses  the  properties  already  noticed 
as  belonging  to  the  coagulated  protein  compounds.  Albumen 
loses  sulphur  in  passing  from  the  soluble  to  the  insoluble  form. 
Heated  with  hydrochloric  acid,  it  assumes  a  blue  color,  which 
inclines  more  to  purple  than  that  of  any  other  protein  compound. 
Boiled  for  a  long  time  in  contact  with  the  atmosphere,  it  gra- 
dually dissolves,  forming  a  non-gelatinizing  fluid  which  contains 
Mulder's  tritoxide  of  protein.  When  treated  with  powerful 
oxidizing  agents,  as  chromate  of  potash  and  sulphuric  acid,  it 
yields  more  acetic  acid,  benzoic  acid,  and  hydride  of  benzoyl, 
and  less  valerianic  acid  than  the  other  protein  compounds. 

The  mean  result  of  five  analyses  by  Scherer,  the  latest  ana- 
lysis by  Mulder,  which  he  regards  as  the  most  exact,  and  one  of 
his  older  analyses  are  subjoined  for  the  sake  of  comparison. 


36  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

Scherer.  Mulder.  Mulder. 


Carbon    . 

.     54.883 

53.5 

54.84 

Hydrogen 

.      7.035 

7. 

7.09 

Nitrogen 

.     15.675 

15.5 

15.83 

Oxygen        ^ 

22. 

21.23 

Sulphur         V 

.     22.365 

1.6 

.68 

Phosphorus  J 

0.4 

.33 

100.0  100.00 

Ruling  estimates  the  albumen  of  the  blood  to  contain  1.325^  of 
sulphur,  that  of  hens'  eggs,  1.748^,  while  Mulder  found  1.3J^  in 
the  former  and  1.6^-  in  the  latter.  Albumen  retains  chloride  of 
sodium  with  such  tenacity  that  it  is  almost  impossible  to  sepa- 
rate it  by  washing.  Its  phosphate  of  lime  usually  amounts  to 
1.6^.  From  its  combination  with  oxide  of  lead,  Mulder  esti- 
mated its  atomic  weight  at  22483.9,  while  from  the  oxide  of 
silver  combination,  he  calculated  it  at  22190.2.  He  supposes 
the  albumen  of  eggs  to  be  composed  of  96.2  protein,  3.2  sul- 
phamide,  and  .6  phosphamide;  and  deduces  the  formula  20(C3q 
H23N,0,o.2HO)  +  8H,NS  +  H,NP. 

Preparation. — The  purest  soluble  albumen  is  obtained  by  neu- 
tralizing serum  or  white  of  egg  dissolved  in  water  with  acetic 
acid,  and  extracting  with  20  or  30  times  the  quantity  of  dis- 
tilled water,  or  with  dilute  spirit.  It  is  usually  prepared  by 
evaporating  serum  or  white  of  egg  in  a  platinum  crucible  in 
vacuo,  or  at  a  temperature  not  exceeding  120°,  pulverizing  the 
yellow  residue,  and  extracting  foreign  matters  first  with  ether 
and  then  with  alcohol. 

Coagulated  albumen  is  obtained  perfectly  pure  by  washing  the 
precipitate  thrown  down  from  white  of  egg  by  hydrochloric  acid, 
with  dilute  hydrochloric  acid,  and  then  dissolving  the  hydro- 
chlorate  in  water,  and  precipitating  it  with  carbonate  of  ammo- 
nia. The  precipitate  is  dried,  pulverized,  and  freed  from  fat  by 
boilins:  it  with  alcohol  and  ether. 

Tests. — Albumen  is  usually  known  by  its  coagulation  on  the 
application  of  heat.  Several  other  agents,  among  which  are 
nitric  acid,  corrosive  sublimate,  and  chromic  acid  also  coagulate 
it.     The  form  of  the  coagulum,  as  already  stated,  will  indicate 


ALBUMINOUS  GROUP. 


37 


the  state  in  which  the  albumen  exists.  At  best,  however,  we 
can  only  approximate  certainty  in  our  recognition  of  this  sub- 
stance. 

In  estimating  albumen  quantitatively,  it  is  necessary  first  to 
neutralize  or  even  slightly  acidulate  the  fluid  with  acetic  acid, 
taking  care  to  avoid  excess  of  this  reagent,  before  attempting  to 
coagulate  it  by  heat,  otherwise  it  will  pass  through  the  filter. 
It  must  be  thoroughly  dried  in  vacuo,  also,  with  the  aid  of 
hygroscopic  substances,  and  cooled  before  weighing,  or  it  cannot 
be  estimated  with  anything  like  certainty. 

Albumen  is  undoubtedly  a  most  important  substance  in  the 
building  up  of  the  economy.  The  general  opinion  among  physi- 
ologists is  that  it  is  transmuted  into  fibrin,  which  becomes  the 
true  plasma  of  all  the  tissues.  Lehmann  supposes  that  albumen 
may  be  directly  converted  into  tissue,  and  suggests  that  the 
necessary  presence  of  fibrin  may  be  accounted  for  on  the  hypo- 
thesis that  this  substance  acts  as  a  sort  of  crystallizing  point  for 
the  albumen. 


FIBRIN. 

This  substance  must  be  studied  in  three  different  modifica- 
tions: 1.  Sohihle  &oxm',  2.  Spontaneoudy  coagulated  &:)vm',  3. 
Fibrin  coagulated  by  means  of  heat;  as  it  has  difi'erent  properties 
in  these  three  distinct  modes  of  existence. 

The    natural    solution    of 


fibrin  is  the  liquor  sanguinis 
of  the  blood.  It  is  precipi- 
tated, along  with  the  albu- 
men, by  concentrated  solution 
of  potash,  but  not  by  acetic 
acid  or  caustic  ammonia. 
Ether  coagulates  fibrin,  but 
not  albumen. 

The  most  striking  peculiar- 
ity of  fibrin  is  its  property  of 
spontaneous  coagulation.  In 
a  short  time  after  blood  has 
been    drawn,    it   divides,    as 


Fis.  1. 


Fig.  1.  Fibrillation  of  fibrin,  as  seen  by  the  mi- 
croscope in  inflammatory  exudation  on  the  peri- 
toueum. 


38  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

every  one  knows,  into  serum  and  clot.  The  clot  is  formed 
by  the  spontaneous  solidification  of  the  dissolved  fibrin,  entan- 
gling blood-corpuscles  in  its  meshes.  The  structural  arrangement 
of  the  clot,  or  rather  the  process  by  which  it  acquires  a  definite 
structure,  has  been  termed  the  fihrillatio7i  of  the  fibrin.  When 
the  fresh  liquor  sanguinis  is  examined  with  the  microscope,  it  is 
found  to  contain  only  a  few  colorless  blood-corpuscles.  After  a 
time,  however,  it  begins  to  assume  a  gelatinous  consistence,  and 
then  several  points  or  molecular  granules  make  their  appear- 
ance in  different  parts  of  the  mass.  From  these,  long  fibrils 
shoot  out,  crossing  one  another,  forming  loops,  and  interlacing 
at  every  possible  angle  till  they  have  woven  a  network  of  fibres. 

Many  attempts  have  been  made  by  chemical  and  physical 
theorists  to  account  for  this  remarkable  property,  but  all  have 
totally  failed.  The  chemical  change,  if  any,  which  fibrin  under- 
goes, in  passing  from  the  soluble  to  the  insoluble  form,  lies 
entirely  beyond  the  range  of  our  present  chemical  knowledge. 
Lehmann  objects  to  the  only  hypothesis  Avhich  the  physiologists 
regard  as  at  all  tenable,  that,  namely,  which  considers  this  a 
vital  change.  He  says  that,  it  is  at  variance  with  all  precon- 
ceived ideas  of  life,  to  attribute  life  to  a  simple  organic  sub- 
stance. The  objection  is  somewhat  unintelligible,  for  the  cell- 
membrane  can  hardly  be  regarded  as  anything  else  than  a 
simple  organic  substance;  and  the  nucleus  envelop  has  been 
generally  conceded  to  be  pure  albumen ;  yet  to  both  of  these 
vitality  is  attributed.  It  matters  not  whether  these  notions  of 
cell  and  nucleus  envelops  are  correct  or  incorrect ;  the  fact  that 
they  are  entertained  is  sufiicient  to  show  that  it  is  not  an  anomaly, 
as  Lehmann  would  have  us  believe,  in  the  present  state  of  physio- 
logy, to  attribute  vitality  to  fibrin. 

Spontaneously  coagulated  fibrin  is  yellow  and  opaque,  be- 
coming hard  and  brittle  in  drying.  It  is  tasteless  and  inodor- 
ous, insoluble  in  water,  merely  absorbing  that  fluid  and  becoming 
soft  and  flexible  again.  It  is  insoluble  also  in  alcohol  and  ether. 
It  decomposes  rapidly,  and  putrefies  in  the  air,  dissolving  if  suf- 
ficient water  be  present,  and  becoming  converted  into  a  substance, 
which,  like  albumen,  is  coagulated  by  heat.  During  this  pro- 
cess it  attracts  oxygen  and  develops  ammonia,  carbonic  acid, 
butyric  acid,  and  sulphuretted  hydrogen,  leaving  a  residue  con- 


ALBUMINOUS  GROUP.  89 

sisting  principally  of  casein  and  tyrosin.  In  a  saline  solution, 
at  a  temperature  of  from  90°  to  100°,  it  forms  a  viscid  solution, 
having  undergone  some  chemical  change.  It  now  coagulates  at 
164°,  and  is  precipitated  by  acetic  acid,  but  not  by  ether. 

The  fibrin  of  venous  is  said  to  differ  from  that  of  arterial 
blood  in  this  latter  reaction.  Scherer  thinks  that  the  fibrin  of 
arterial  or  of  inflammatory  venous  blood  does  not  undergo  this 
change.  This  has  been  denied,  but  the  question  is  not  yet 
settled. 

Boiled  fibrin  closely  resembles  coagulated  albumen.  Its  spe- 
cific gravity,  after  deducting  for  the  ash,  is  1.2678.  It  is  no 
longer  capable  of  decomposing  peroxide  of  hydrogen,  nor  of 
being  converted  into  an  albumen-like  substance  by  digestion 
in  solutions  of  alkaline  salts.  Boiled  a  long  time  in  water,  it 
gives  rise  to  a  soluble  and  an  insoluble  substance,  the  teroxide 
and  binoxide  of  protein  of  Mulder.  Decomposed  by  oxidating 
reagents,  it  yields  more  butyric  acid  than  any  of  the  protein- 
compounds,  but  less  acetic  and  benzoic  acids  than  albumen. 

Comijosition. — Fibrin  has  never  yet  been  obtained  pure,  being 
mixed  with  white  blood-corpuscles,  and  manifestly  containing 
several  organic  compounds.  The  following  analyses  are  the 
latest  that  have  been  published: — 

Carbon  ..... 
Hydrogen  .... 
Nitrogen         .... 

Oxygen        ^ 

Sulphur         y  .          .         . 

Phosphorus  J 

100.000  100.0 

Dry  fibrin  contains  about  2.6  per  cent,  of  fats  combined  with 
ammonia  and  lime.  Mulder  found  1.7^,  Virchow  0.66^  of 
phosphate  of  lime  in  it.  It  is  generally  supposed  that  it  con- 
tains more  oxygen  than  albumen.  Mulder,  therefore,  regards 
it  as  a  higher  degree  of  oxidation  of  protein,  combined  with 
sulphamide  and  phosphamide.  His  formula  for  it  is  (CggHg^N^O^j. 
2HO)H2NS-l-H2NP. 


Scherer. 

Mulder. 

53.571 

52.7 

6.895 

6.9 

15.720 

15.4 

/23.5 

22.814 

J    1.2 

I   0.3 

40  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

Mulder's  hinoxide  of  protein  is  obtained  in  a  variety  of  ways, 
among  which  we  may  mention  the  protracted  boiling  of  fibrin  in 
water,  with  free  exposure  to  the  atmosphere,  and  precipitating 
with  acetic  acid.  It  is  a  light-yellow,  lumpy,  tough  precipitate, 
drying  to  a  blackish-green,  shining,  resinous  mass.  Mulder's 
formula  is  6(C36H,3N,0„.2HO)  +  S20,. 

Preparation. — The  natural  solution  of  fibrin  is  obtained  by 
allowing  fresh  frog's  blood  to  flow  into  sugared  water  and 
filtering  off  the  clear  fluid.  To  obtain  spontaneously  coagulated 
fibrin,  a  blood  clot  is  cut  into  fine  pieces  and  washed  till  it  is 
white.  Or  it  may  be  obtained  by  whipping  coagulating  blood 
with  rods  or  agitating  it  in  a  bottle  with  shot,  and  then  suspend- 
ing it,  in  a  bag  in  water,  till  it  is  thoroughly  washed.  Pure 
boiled  fibrin  is  obtained  by  drying  it,  then  extracting  it  with 
alcohol  acidulated  with  sulphuric  acid,  and  finally  with  ether. 

Tests. — Fibrin  is  usually  recognized  by  its  microscopic  cha- 
racters and  by  its  reaction  with  alkaline  salts.  The  quantitative 
estimation  of  this  substance  is,  for  the  reasons  already  men- 
tioned, extremely  difficult.  An  approximative  estimation  is  the 
most  that  can  be  made.  This  is  usually  accomplished  by  whip- 
ping fresh  blood  and  purifying  and  drying  it,  in  the  manner 
already  described. 

Fibrin  is  found  chiefly  in  the  blood,  lymph,  and  chyle.  Its 
proportion  varies  considerably  even  in  diflferent  vessels.  Its 
range  is  from  about  0.2  to  0.3  per  cent,  in  venous  blood.  The 
portal  vein  contains  less  than  the  jugular,  and  the  veins  remote 
from  the  heart  generally  more  than  those  near  it.  The  blood 
of  new-born  infants  contains  less  fibrin  than  that  of  adults,  the 
increase  of  this  element  being  especially  conspicuous  at  the  age 
of  puberty.  In  pregnancy,  fibrin  increases,  particularly  during 
the  last  three  months.  Lehmann  and  Nasse  found  that  the 
quantity  of  fibrin  was  greater  during  an  animal  than  during  a 
vegetable  diet.  According  to  the  latter  observer,  fibrin  is  in- 
creased during  fasting.  Herbivorous  animals  are  said  to  have 
more  of  this  element  in  their  blood  than  the  carnivorous,  and 
birds  more  than  either. 

In  disease,  rheumatism  and  inflammation  increase  it.  The 
quantity  of  it  in  the  lymph  of  man  is  stated  at  0.052^. 


ALBUMINOUS  GROUP.  41 

There  has  been  much  question  recently  in  reference  to  the 
origin  of  fibrin,  but  it  has  been  now  pretty  generally  conceded 
to  be  formed  from  albumen.  The  question  also  has  been  asked 
whether  fibrin  is  the  result  of  a  progressive  or  regressive  meta- 
morphosis, i.  e.  whether  it  is  always  a  stage  between  albumen 
and  fully  developed  tissue,  according  to  the  old  physiological 
view,  or  whether  it  is  a  step  towards  decay  and  elimination. 
That  fibrin  is  a  body  of  a  higher  degree  of  oxidation  than  albu- 
men is  universally  admitted;  but,  as  Lehmann  urges,  it  con- 
tains less  oxygen  than  the  tissues.  He  is  therefore  inclined  to 
believe  that  it  is  a  transition  stage,  and  may  on  the  one  side 
ascend  into  tissue,  or  on  the  other,  descend  into  excretion.  In 
inflammation,  he  thinks,  owing  to  the  diminished  supply  of  oxy- 
gen, in  consequence  of  the  imperfect  action  of  the  lungs,  albu- 
men is  unable  to  pass  into  the  higher  degrees  of  oxidation,  but 
is  arrested  at  this  lower  stage,  whence  the  quantity  of  fibrin  in 
the  blood  is  necessarily  increased.  He  says :  "  The  frequent 
but  short  and  incomplete  respirations  which  occur  only  in  febrile 
(and  not  in  non-febrile)  inflammations  are  only  sufficient  to  con- 
vey to  the  blood  sufficient  oxygen  to  convert  certain  substances 
into  fibrin,  but  not  to  oxidate  them  farther ;  this  is  the  reason 
why  the  amount  of  fibrin  attains  its  maximum  in  pneumonia  and 
pleuritis,  and  why  the  blood  in  the  former  disease  is  most  rich 
in  carbonic  acid,  for  this  gas  is  scantily  excreted  in  proportion 
as  oxygen  is  scantily  received  in  the  lungs." 

Muscular  fibrin  has  been  recently  shown  to  be  a  difi"erent 
substance  from  the  true,  or  blood  fibrin  just  described.  It  is 
precipitated  from  the  hydrochloric  solution  of  flesh,  by  neutral- 
ization, as  a  coherent,  elastic,  snow-white  mass,  which  may  be 
detached  in  membranes,  and  presents  under  the  microscope, 
when  tension  is  used,  characters  analogous  to  those  of  blood 
fibrin.  Chloride  of  calcium  and  sulphate  of  magnesia  precipi- 
tate it  only  after  boiling.  Nitric  acid  and  chromic  acid  throw 
it  down,  while  hydrochloric  acid  in  excess  only  clouds  its  alka- 
line solution.  Uncoagulated  S7/ntonin,  as  this  substance  is  now 
called,  is  insoluble  in  nitre.  Besides  all  these  peculiarities,  it 
differs  slightly  from  fibrin  in  chemical  composition. 


42  PKINCIPLES  OF  ANIMAL  CHEMISTRY. 


GLOBULIN. 

This  substance,  whicli  has  also  received  the  name  of  cri/stalUn, 
occurs  naturally  in  the  soluble  state,  but  becomes  insoluble  by 
boiling.  The  soluble  form,  dried  at  120°,  is  yellowish,  trans- 
parent, and  easily  reduced  to  a  snow-white  powder.  It  is  taste- 
less and  inodorous,  swells  in  water,  like  albumen,  and  gradually 
dissolves.  It  is  precipitated  by  alcohol,  and  then  is  insoluble 
in  water,  but  partially  soluble  in  boiling  alcohol.  It  is  distin- 
guished from  albumen  by  its  solution  not  becoming  opalescent  at 
a  lower  temperature  than  164°.  At  182°  it  becomes  milky, 
and  at  199°  separates  as  a  globular  mass  or  as  a  milky  coagu- 
lum.  It  is  not  precipitated  by  acetic  acid  or  by  ammonia;  but, 
when  treated  with  one  of  these  reagents  and  neutralized  with  the 
other,  it  becomes  turbid.  It  decomposes  more  readily  than  the 
other  protein  compounds,  and  when  boiled,  it  develops  ammonia. 

Compositmi. — Globulin  from  the  crystalline  lens  gave  the 
following  results  to  Mulder  and  Riiling: — 

Mulder.  Riiling. 

Carbon 54.5  54.2 

Hydrogen      .....       6.9  7.1 

Nitrogen 16.5  f  37  5 

Oxygen  "I                                                  ^.^  I       • 

Sulphur] ^""  1.2 


100.0  100.0 

Berzelius  supposed  globulin  to  contain  phosphorus.  Mulder 
found  none,  but  only  sulphur  in  the  proportion  of  0.265§. 
Lehmann  makes  it  1.134^,  and  Riiling  1.227^. 

It  is  prepared  by  neutralizing  the  fluid  of  the  crystalline  lens 
with  acetic  acid,  evaporating  to  dryness  at  a  temperature  not 
exceeding  120°,  and  extracting  with  ether  and  dilute  alcohol. 
Coagulated  globulin  is  procured  by  extracting  the  precipitate 
obtained  by  boiling  with  water,  alcohol,  and  ether,  and  by 
precipitating  with  hydrochloric  acid  and  washing  thoroughly. 

In  the  cells  of  the  crystalline  lens  is  a  fluid  which  contains 
35.92-  of  dry  globulin.     It  is  also  one  of  the  principal  con- 


ALBUMINOUS  GROUP.  43 

stituents  of  the  blood,  forming,  with  hematin,  the  viscid  fluid 
contained  in  the  red  corpuscles. 

It  is  thought  to  be  formed  by  the  action  of  the  walls  of  the 
corpuscles  upon  the  albumen  of  the  blood,  and  seems  to  be  albu- 
men modified  by  oxidation,  and  to  hold  an  intermediate  place 
between  this  substance  and  fibrin.  It  has  been  supposed  by  some 
to  be  directly  converted  into  fibrin,  but  of  this  there  can  be  no 
certainty  in  the  present  state  of  chemical  science. 

The  use  of  globulin  in  the  crystalline  lens  is  to  attain  an 
achromatic  apparatus,  by  introducing  a  substance  of  different 
refracting  power  from  the  membranous  portion  of  the  lens.  It 
is  also  worthy  of  note  that  nature  has  not  relied  alone  upon  the 
anatomical  structure  of  the  lens,  but  has  increased  the  density 
of  the  globulin  itself  from  the  surface  to  the  centre  of  this 
organ.  Thus  a  lens  weighing  30  grains,  taken  from  the  eye  of 
an  ox,  had  a  specific  gravity  of  1.0765,  while  the  centre,  weigh- 
ing 6  grains,  was  1.194.  This  globulin  is  separated,  entirely 
free  from  hematin,  from  the  blood  of  the  minute  capsular  artery 
by  the  lens. 

The  use  of  globulin  in  the  blood-corpuscles  is  entirely  un- 
known. 

CASEIN. 

Soluble  casein  when  dry  is  an  amber-yellow,  inodorous,  insipid, 
viscous  mass,  neither  acid  nor  alkaline.-  It  dissolves  in  water 
to  a  yellowish,  viscid  fluid,  which,  on  evaporation,  is  covered  by 
a  white  film  of  insoluble  casein.  Exposed  to  the  air,  it  putrefies, 
developing  ammonia,  leucin,  tyrosin,  &c. 

Alcohol  renders  casein  opaque,  and  dissolves  a  small  portion 
of  it,  which  may  be  obtained  in  an  unchanged  state  by  evapora- 
tion. Boiling  alcohol  dissolves  more  of  it,  but  lets  it  fall  on 
cooling.  This  reagent  precipitates  casein  from  a  concentrated 
aqueous  solution,  but  the  precipitate  retains  its  solubility  in 
water,  unless  a  large  quantity  of  strong  alcohol  has  been  added. 

Boiling  does  not  coagulate  casein  from  its  solutions.  Acids 
throw  it  down  and  partially  combine  with  it,  but  on  neutraliza- 
tion with  alkalies  it  again  dissolves,  and  the  precipitate  is  solu-. 


44  PRINCIPLES  OP  ANIMAL  CHEMISTRY. 

ble  in  both  pure  water  and  alcohol.  It  is  distinguished  from 
albumen  by  the  fact  that  acetic  and  lactic  acids  precipitate  it. 
Alcohol  dissolves  its  precipitates,  and  the  alcoholic  solution  can- 
not, of  course,  be  precipitated  by  acids.  Tannic  acid  throws  it 
down  from  all  solutions.  Its  products  of  decomposition  are  the 
same  as  those  of  albumen  and  fibrin.  The  alkaline  earths  and 
their  salts  on  the  application  of  heat  precipitate  it.  31etallic 
salts  throw  it  down,  and  form  with  it  two  sets  of  compounds,  one 
containing  the  acid,  the  other  the  base. 

When  obtained  free  from  alkalies,  its  reactions  are  somewhat 
dijQTerent.  It  is  very  slightly  soluble  in  water,  and  not  at  all  in 
alcohol.  It  reddens  blue  litmus  paper,  and  forms  solutions  with 
carbonate  and  phosphate  of  soda,  which  no  longer  exhibit  an 
alkaline  reaction.  It  dissolves  in  many  neutral  alkaline  salts, 
does  not  coagulate  on  boiling,  but  forms  the  film  already  de- 
scribed. It  dissolves  in  dilute  mineral  acids,  but  is  precipitated 
by  excess  of  these  reagents,  and,  on  evaporation,  the  acid  solu- 
tion is  covered  with  the  same  precipitate  in  the  form  of  a  color- 
less, transparent,  and  toughish  membrane.  Heat  alone  does 
not  coagulate  casein,  but  if  carbonate  of  potash  or  nitre  with  a 
little  potash  be  added,  and  the  solution  neutralized,  a  copious 
thick  coagulum  is  formed  when  the  solution  is  boiled. 

Casein  is  coagulated  by  exposure  to  the  air  and  by  the  action 
of  rennet,  the  mucous  membrane  of  the  calf's  stomach.  In  the 
first  instance,  it  is  precipitated  by  the  lactic  acid,  formed  by  the 
action  of  the  air  on  the  sugar  of  the  milk.  In  the  latter  case, 
Simon  and  Liebig  supposed  that  the  rennet  acted  as  a  ferment, 
hastening  this  same  oxidation.  Selmi's  experiments  are  opposed 
to  this  view;  showing,  as  they  do,  that  the  alkaline  reaction 
remains  after  the  coagulation  has  taken  place,  so  that  the  cause 
of  this  change  is  still  enveloped  in  obscurity.  Scherer's  expe- 
riments show  that  it  cannot  take  place  without  the  presence  of 
oxygen. 

The  researches  of  Mulder  and  Schlossberger  have  rendered  it 
probable  that  this  substance  is  composed  of  several  distinct 
bodies. 

Coagulated  casein  is  hard,  yellowish,  and  translucent.  It 
swells,  but  does  not  dissolve  in  water,  and  is  insoluble  in  alcohol. 


ALBUMINOUS  GROUP.  45 

It  combines  with  acids  and  alkalies,  and  resembles  coagulated 
albumen  in  its  relations  to  the  mineral  acids.  When  heated,  it 
softens,  becomes  ductile  and  elastic,  and  at  a  higher  tempera- 
ture it  fuses,  carbonizes,  and  gives  off  the  same  substances  as 
albumen  and  fibrin  under  similar  circumstances.  During  putre- 
faction, it  develops  first  carbonate  and  hydrosulphate  of  ammo- 
nia, and  then  valerianic  and  butyric  acids,  leucin,  a  white, 
crystallizable,  sublimable  body,  having  a  strong  fecal  odor,  and 
an  acid,  which,  when  decomposed  with  a  mineral  acid,  yields  a 
brown  substance,  tyrosin  and  ammonia. 

The  coagulum  obtained  from  woman  s  milk,  differs  from  that 
of  cow's  milk  in  being  soluble  in  water,  loose,  and  jelly-like,  and 
deliquescent.  Lehmann  thinks  that  these  differences  depend 
upon  the  greater  alkalinity  of  woman's  milk. 

Composition. — The  following  analyses  of  casein  are  from 


Carbon    . 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 


Mulder,  Scherer,  and  Dumas. 


53.83 

54.665 

53.7 

7.15 

7.465 

7.2 

15.65 

15.724 

16.6 

23.37 

22.146 

22.5 

100.00  100.000  100.0 


Recent  investigations  establish  the  percentage  of  sulphur  in 
purified  casein  at  0.85.  Casein  that  has  not  been  treated  with 
acids  contains  about  6^  of  phosphate  of  lime. 

Mulder  regards  this  substance  as  a  compound  of  protein  and 
sulphamide,  but  has  abandoned  his  old  formulae,  and  proposed 
no  new  one,  because  of  the  uncertainty  still  existing  in  regard 
to  its  being  a  simple  substance. 

Preparation. — Soluble  casein  is  obtained  in  a  variety  of  ways. 
We  shall  only  cite  Rochleder's  method  of  procuring  it  free  from 
alkali. 

Skimmed  milk  is  coagulated  with  dilute  sulphuric  acid,  the 
precipitate  pressed  and  dissolved  in  a  solution  of  carbonate  of 
soda.  This  solution  is  allowed  to  stand  for  some  time  in  a  shal- 
low vessel,  and  the  fat  that  forms  on  the  surface  is  skimmed  off 


46  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

with  a  spoon,  or  the  subjacent  fluid  is  decanted  by  means  of  a 
siphon.  This  solution  is  again  precipitated  with  an  acid,  and 
subjected  to  the  same  treatment.  After  this  process  has  been 
gone  through  three  times,  the  remainder  of  the  fat  is  extracted 
with  alcohol  and  ether.  Repeated  boiling  in  water  entirely 
separates  all  the  acid,  and  casein  is  obtained  in  its  purest 
possible  form. 

Tests. — Recent  examinations  have  shown  that  the  old  tests 
for  casein,  its  conversion  into  a  pellicle,  its  precipitability  by 
acetic  acid,  &c.,  must  be  abandoned,  as  they  are  not  at  all 
diagnostic. 

When  rennet  is  used,  it  is  necessary  first,  that  it  should  be 
fresh ;  and  then,  that  it  should  be  digested  in  the  fluid  at  a 
temperature  of  104°  for  not  longer  than  two  hours.  Should  no 
coagulum  then  be  formed,  casein  is  probably  absent. 

Lehmann's  method  is  first  to  add  hydrochlorate  of  ammonia, 
in  order  to  get  rid  of  albuminate  of  soda;  to  filter;  then  to  add 
sulphate  of  magnesia  and  chloride  of  calcium  ;  to  filter  again,  if 
a  precipitate  falls  from  the  cold  solution;  then  to  boil  it,  and,  if 
a  precipitate  form,  to  determine  its  nature  by  rennet. 

The  best  quantitative  process,  according  to  Lehmann,  is  that 
proposed  by  Haidlen.  He  stirs  milk  with  one-fifth  of  its  weight 
of  finely  pulverized  gypsum,  heats  it  to  212°,  and  removes  the 
fat,  milk-sugar,  and  most  of  the  salts  by  means  of  ether  and 
alcohol.  The  residue  is  not  pure  casein,  but  the  quantity  of 
that  ingredient  is  easily  ascertained,  by  determining  the  pro- 
portion of  fat,  sugar,  and  salts  contained  in  the  milk. 

Physiological  Relations. — Casein  occurs  in  the  milk  of  all  the 
mammalia.  In  women's  milk,  of  good  quality,  Haidlen  found 
3.1^;  in  inferior  milk  only  2.7|5.  In  cow's  milk,  the  propor- 
tion has  been  variously  computed,  at  from  3 J*  to  755;  ^"^  asses' 
milk,  at  from  1.955  to  2.3^  ;  and  in  goat's  milk,  at  from  4.52^ 
to  9.66^.  According  to  Dumas  and  Bensch,  an  animal  diet 
increases  the  quantity  of  casein. 

It  is  found  partly  in  solution  and  partly  in  the  wall  of  the 
milk-globules.  The  presence  of  an  investing  membrane  around 
the  milk-globules  is  beautifully  shown  by  an  experiment  devised 
by  Mitscherlich.     On  shaking  fresh  milk  with  ether,  scarcely 


ALBUMINOUS  QKOUP.  47 

any  fat  is  taken  up,  but  on  adding  some  substance  capable  of 
destroying  cell-walls  a  great  quantity  of  fat,  all  indeed  that  the 
milk  contains,  "will  be  dissolved  by  the  ether.  The  microscope 
shows  that  milk-globules,  acted  on  by  ether  without  the  addition 
of  caustic  alkali,  become  opaque,  corrugated,  and  transparent, 
showing  that  the  ether  has  coagulated  the  cell-wall.  Sulphate 
of  soda  bursts  the  capsule  of  the  globules,  and  allows  the  ether 
to  get  free  access  to  the  contained  fat,  and  the  microscope  then 
discovers  minute  granules,  the  fragments  of  the  broken  up  cor- 
puscles floating  in  the  fluid.  "Hence,"  says  Lehmann,  "we 
perceive  that  our  ordinary  casein  not  only  contains  the  protein- 
compound  dissolved  in  the  milk,  but  likewise  another,  which 
forms  the  capsule  of  the  milk- corpuscles,  so  that  we  thus  also 
have  a  microscopico-mechanical  proof  of  the  composite  nature 
of  ordinary  casein." 

The  origin  of  casein  is  entirely  unknown.  It  probably  exists 
in  the  blood,  and  is  only  eliminated  from  it  by  the  mammary 
glands.     Its  relations  to  albumen  have  not  been  determined. 

"The  occurrence  of  casein  in  the  milk,  the  best  of  all  kinds  of 
food,  leaves  no  doubt  regarding  the  uses  of  this  substance,  espe- 
cially since  we  see  how  nature  provides  that  more  casein  is 
always  supplied  for  the  building  of  the  bodies  of  very  young 
animals  than  is  required  for  their  future  support.  Casein  not 
only  yields  to  the  infant  body  the  material  by  which  soft  parts 
are  nourished  and  caused  to  grow,  but  likewise  conveys  into  the 
system  a  sufiicient  quantity  of  bone-earth  and  lime  to  cause  the 
skeleton  of  the  infant  body  gradually  to  attain  its  necessary 
solidity."* 

There  are  vegetable  substances  intimately  related  to  this  pro- 
tein group,  of  great  consequence  as  nutritive  substances,  which 
shall  now  be  glanced  at. 

GLUTEN. 

When  dried,  this  substance  is  transparent,  hard,  and  difficult 
to  pulverize.     When  moist,  it  is  adhesive,  viscid,  and  elastic.    It 

*  Lehmann's  Physiological  Chemistry. 


48  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

is  insoluble  in  cold,  and  but  slightly  soluble  in  hot  water ;  easily 
soluble  in  boiling  alcohol,  from  which  it  is  precipitated  by  water, 
by  corrosive  sublimate,  and  by  acetate  of  lead.  It  does  not 
dissolve  readily  in  acetic  acid,  but  in  other  respects  possesses 
all  the  properties  of  protein  compounds. 

Composition. — Analyses  of  this  compound  vary  greatly.     We 
copy  those  of 

Scherer,  and  Mulder. 

Carbon 54.6  54.84 

Hydrogen 7.4  7.05 

Nitrogen 15.8  15.71 

Oxygen  |  9^  o  21.80 

Sulphur/ ""*"  0.60 


100.0  100.00 

Ruling  found  1.134^  of  sulphur  in  wheat-gluten,  and  Verdeil 
0.985^  in  rye-gluten. 

Prejyaration. — It  is  obtained  by  kneading  flour  under  water, 
boiling  the  residue  with  alcohol  to  extract  starch,  filtering  while 
hot,  and  cooling  and  evaporating  the  solution,  when  it  is  preci- 
pitated in  white  flocculi. 

LEGUMIN. 

This  substance  forms  either  a  nacreous,  iridescent  precipitate, 
or  falls  in  flocculi.  When  dried,  it  is  yellow,  transparent,  and 
brittle.  It  coagulates,  like  albumen,  from  its  aqueous  solution, 
but  is  precipitated,  like  casein,  by  acetic  and  phosphoric  acids. 
It  does  not,  however,  dissolve  in  concentrated  acetic  acid.  It  is 
coagulated  by  rennet.  It  dissolves  readily  in  ammonia  and  the 
other  alkalies. 

Composition. — The  analyses  of  this  substance  vary  so  much 
that  it  is  evidently  an  impure  preparation  which  has  been 
analyzed.     The  following  are  the  results  obtained  by 


Carbon  . 

Hydrogen 

Nitrogen 

Oxygen 

Sulphur 


ALBUMINOUS  GROUP.  49 

Dumas  and  Cahours,  and  Rochleder. 


50.50 

56.24 

6.78 

7.97 

18.17 

15.83 

24.55 

19.96 

100.00  100.00 


Preparation. — Legumin  is  found  in  peas  and  beans,  and  is 
obtained  by  making  a  watery  extract  of  these  seeds.  This 
extract  is  acid,  and  on  neutralization,  the  legumin  is  precipi- 
tated. It  is  purified  by  solution  in  ammonia,  precipitation  by 
an  acid,  and  digestion  in  alcohol  and  ether. 

TEROXIDE  OF  PROTEIN. 

This  is  a  brittle  substance  when  dry ;  but,  in  a  moist  state,  it 
is  tough,  viscid,  and  ductile.  When  warmed,  it  smells  like  gela- 
tin. It  is  soluble  in  water,  but  insoluble  in  alcohol  and  ether. 
It  is  precipitated  by  dilute  mineral  acids,  chlorine,  tannic  acid, 
corrosive  sublimate,  salts  of  lead,  silver,  zinc,  and  iron,  but  not 
by  ferrocyanide  of  potassium,  the  alkaline  salts,  or  chloride  of 
barium.  With  alkalies  it  forms  neutral  compounds,  from  which 
it  is  precipitated  by  metallic  salts.  Boiled  with  caustic  potash, 
it  develops  ammonia,  and  is  converted  into  a  substance  which, 
according  to  Mulder,  is  a  true  teroxide  of  protein  (C3gH25N40jo-|- 
30  +  3HO). 

Composition. — Mulder  supposes  this  substance  to  be  a  combi- 
nation of  the  true  teroxide  of  protein  with  ammonia,  and  gives 
the  formula  H,NO  +  2(C36H2,N,Oj3)  +  3HO. 

Tests. — These  are  not  yet  fully  determined  upon. 

Physiological  Relations. — It  exists,  according  to  Mulder,  in 
normal  blood  and  in  pus,  as  well  as  in  all  fluid  exudations.  Its 
quantity  in  the  blood  is  increased  in  inflammatory  disease.  He 
regards  the  p>yin  of  Guterbock  as  identical  with  this  compound. 
"  If,"  says  Lehmann,  "  more  accurate  investigations  confirm  the 
existence  of  this  teroxide  of  protein  in  the  manner  that  Mulder 
supposes,  we  shall  then  acquire  a  knowledge  of  an  important 
4 


50  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

intermediate  link  in  the  metamorphosis  of  the  animal  tissues; 
and,  in  particular,  Tve  shall  have  considerably  approximated  to 
the  yet  unsolved  problem  of  the  conversion  of  albuminous  bodies 
into  bodies  yielding  gelatin,  or  of  fibrin  into  tissue." 


CHAPTER    IV. 

THE  GELATINOUS  GROUP. 

Gelatin  does  not  exist  ready  formed  in  the  organism,  but  is 
produced  by  boiling  certain  parts  with  water.  It  is  distinguished 
from  other  animal  substances  by  its  property  of  swelling  and 
becoming  translucent  in  cold  water  and  dissolving  in  hot ;  and 
by  its  reaction  with  chlorine,  tannic  acid,  and  the  metallic  and 
earthy  salts. 

There  are  two  prominent  varieties  of  gelatin,  hone-gelatin, 
glue  or  glutin,  and  cartilage-gelatin  or  ehondrin. 

glutin. 

Pure  glutin  occurs  in  colorless,  transparent  pieces,  which  are 
hard,  horny,  brittle,  inodorous,  insipid,  heavier  than  water,  and 
which  do  not  stick  to  the  pestle  like  the  protein  compounds, 
when  triturated. 

In  cold  water  it  softens,  in  warm  water  it  forms  a  viscid  solu- 
tion which  cools  to  a  jelly.  After  repeated  solution  in  hot 
water,  it  no  longer  gelatinizes  on  cooling.  Gelatinized  glutin 
becomes  acid  on  exposure  to  the  air,  and  loses  its  tenacity.  It 
is  insoluble  in  alcohol,  ether,  fats,  and  volatile  oils. 

Acids^  with  the  exception  of  the  tannic,  do  not  precipitate  it. 
Alkalies  only  throw  down  a  little  bone-earth,  which  is  often 
mixed  with  it.  The  only  metallic  salts  which  precipitate  it  are 
the  bichloride  and  sulphate  of  the  binoxide  of  platinum,  corro- 
sive sublimate,  and  the  basic  sulphate  of  binoxide  of  iron.  The 
latter  throws  down  a  bulky  precipitate,  which  becomes  deep  red 


THE  GELATINOUS  GROUP.  51 

by  drying.  Ferrocyanide  of  potassium  does  not  affect  its  solu- 
tion. Chlorine  separates  a  thready  coagulum.  Creasote  ren- 
ders the  solution  milky. 

Dry  gelatin,  when  heated,  swells  up,  emits  the  odor  of  burned 
horn,  does  not  catch  fire  easily,  burns  for  but  a  short  time,  and 
leaves  a  voluminous,  blistered,  shining  coal. 

Boiled  with  concentrated  nitric  acid,  it  is  converted  into  oxalic 
and  saccharic  acids,  and  into  two  substances  resembling  suet  and 
tannic  acid.  With  sulphuric  acid,  it  forms  a  solution  which,  on 
boiling,  yields  leucine,  glycine,  &c.  With  chromic  acid,  it  fur- 
nishes most  of  the  non-nitrogenous  acids,  with  nitriles  and  alde- 
hydes. Boiled  with  hydrated  potash,  it  develops  ammonia,  and 
is  decomposed  into  leucine  and  glycine. 

Composition. — Glutin  yields  according  to 

Mulder,  and   Scherer. 

Carbon 60.40  50.76 

Hydrogen 6.64  7.15 

Nitrogen 18.34  18.32 

Oxygen 24.62  23.77 


100.00  100.00 

Mulder's  formula  is  Ci3H,oN205;  Liebig's  C^jH^oNgOjo-  Schlei- 
fer  found  from  0.12  to  0.14  per  cent,  of  sulphur  in  glutin  from 
bones  and  ivory. 

Preparation. — Berzelius  obtained  glutin  from  common  glue, 
by  softening  it  in  water,  subjecting  it  repeatedly  to  strong  pres- 
sure, suspending  it  in  a  bag  in  cold  water  till  everything  soluble 
was  taken  up,  and  then  heating  it  to  122°.  The  solution  thus 
obtained  was  rapidly  filtered  while  still  hot.  Pure  glutin  can 
only  be  obtained  from  cellular  tissue,  shavings  of  hartshorn, 
calves'  feet,  and  the  swimming  bladder  of  certain  fishes.  These 
are  boiled  till  they  are  thoroughly  dissolved,  filtered  whilst  still 
hot,  and  the  resulting  impure  glutin  treated  according  to  the 
method  of  Berzelius  just  described. 

Combinations. — When  chlorine  gas  is  passed  through  a  solu- 
tion of  glutin,  each  bubble  of  gas  is  enveloped  in  a  glutinous 
capsule;  the  fluid  becomes  milky ;  white  flakes  appear ;  and  at 


52 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


the  bottom  of  the  vessel  is  deposited  a  semitransparent  jelly. 
The  white  substance  is  a  chlorite  of  glutin. 

The  action  of  acids  on  glutin  is  imperfectly  known.  With  dilute 
mineral  acids,  it  forms  combinations,  which,  on  cooling,  behave 
like  pure  glutin.  Concentrated  acetic  acid  dissolves  glutin  which 
has  been  softened  in  water,  and  deprives  it  of  its  property  of 
gelatinizing  on  cooling.  The  precipitate  with  tannic  acid,  accord- 
ing to  Mulder,  consists  of  three  equivalents  of  glutin  and  two 
of  tannic  acid=  C39H3oNgOj3+  CggHj.Ogj. 

Glutin  combines  with  several  basic  salts.  A  very  consider- 
able quantity  of  bone-earth  dissolves  in  a  solution  of  glutin. 
Treated  with  alum  and  with  sulphate  of  the  peroxide  of  iron, 
glutin  yields  a  precipitate  after  the  addition  of  an  alkali. 

Physiological  Relations. — Glutin  is  obtained  from  bones,  ten- 
dons, skin,  and  permanent  cartilages  when  they  become  ossi- 
fied from  disease.  The  conversion  of  the  basis  of  these  parts 
into,  glutin  goes  on  without  any  evolution  of  gas  or  other  signs 
of  chemical  action,  and  seems  to  consist  only  of  a  change  of 
molecular  constitution. 

Gelatin  is  thus  an  essential  part  of  the  passive  and  protective 
parts  of  the  organism,  and  does  not  enter  into  the  formation  of 
its  active  parts. 

CHONDRIN. 

When  dry,  chondrin  is  a  transparent,  horny,  glistening  mass, 
more  colorless  than  glutin,  from  which  it  differs  in  its  reactions 
with  acids  and  the  metallic  salts.  The  former  and  many  of  the 
latter  precipitate  it.  Salts  of  alumina  throw  down  white,  com- 
pact flocks,  which,  on  drying,  cake  together;  they  are  insoluble 
in  water,  but  dissolve  in  excess  of  the  earthy  salt,  as  well  as  in 
chloride  of  sodium,  and  the  alkaline  acetates. 
Composition, — It  contains  according  to 


Mulder, 

Scherer. 

Carbon     . 

.     49.97 

50.754 

Hydrogen 

.       6.63 

6.904 

Nitrogen  . 

.     14.44 

14.692 

Oxygen    . 
Sulphur    . 

.     28.59 
.       0.38 

1  27.650 

100.00 


100.000 


NITROGENOUS  BASIC  BODIES.  63 

Mulder's  formula  is  Cj^Ij^N^Oi/,  Scherer's,  C48H4oNg02o. 

Preparation. — Chondrin  is  obtained  by  boiling  the  permanent 
cartilages  in  water,  for  eighteen  or  twenty-four  hours.  It  is 
purified  in  the  same  manner  as  glutin,  and  the  dried  residue 
is  extracted  with  alcohol. 

Physiological  Relations. — It  is  found  in  all  healthy  permanent 
cartilages,  and  in  the  temporary  cartilages  before  ossification. 
Sometimes  it  is  found  in  diseased  bone.  It  is  probable  that 
glutin  is  formed  from  it. 

There  are  other  varieties  of  gelatin  different  from  these  two; 
that,  namely,  which  is  obtained  from  bone  altered  by  osteo- 
malacia, and  that  which  is  procured  from  the  elastic  coat  of 
arteries. 


CHAPTER    V. 

NITROGENOUS  BASIC  BODIES, 

There  are  obtained  from  the  animal  body  many  nitrogenous 
substances  which  are  not  histogenetic,  that  is,  which  have  no 
share  in  the  process  of  nutrition  or  the  construction  of  tissues. 
Most  of  them,  nevertheless,  are  important  to  the  well-being  of 
the  creature,  because  they  form  essential  constituents  of  secre- 
tions, or  constitute  intermediate  stages  between  the  tissues  and 
the  excretions. 

These  substances  are  true  alkaloids  capable  of  forming  salts 
with  acids.  Many  of  them  have  sufficiently  powerful  basic  pro- 
perties to  precipitate  the  heavy  metals  from  their  salts,  and  even 
to  liberate  ammonia. 

They  are  divided  into  two  very  natural  groups,  the  non- 
oxj^genous  and  the  oxygenous  alkaloids. 

The  bodies  of  the  first  class  do  not  exist  as  such  in  the  human 
body,  but  are  obtained  by  the  destructive  distillation  of  the 
gelatinous  tissues.  There  are  three  of  them  obtained  from  these 
tissues;  aniline, picoline,  a.nd  petinine.    They  are  highly  refract- 


54 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


ing,  colorless  fluids,  pungent  in  their  smell  and  taste.     They 
have  no  physiological  interest. 

The  oxygenous  alkaloids  are  more  interesting.  Many  of  them 
exist  already  in  the  economy,  and  nearly  all  of  them  throw  some 
light  upon  those  vital  processes  which  lie  beyond  the  range  of  ordi- 
nary research.  Their  basicity  varies  greatly,  and  no  direct  rela- 
tion has  yet  been  detected  between  their  atomic  constitution  and 
their  saturating  capacity.  They  are  nearly  all  crystallizable, 
inodorous,  soluble  in  alcohol,  and  usually  bitter  in  taste. 


CREATINE. 

When  finely  chopped  flesh  is  thoroughly  kneaded  in  water, 
and  subjected  to  powerful  pressure,  a  liquid  is  obtained  which 
contains  salts  and  several  animal  substances.  Coagulable  mat- 
ters being  removed  by  boiling  and  the  phosphates  by  caustic 
baryta,  the  fluid  is  to  be  evaporated  to  one-twentieth  of  its  bulk, 
care  being  taken  to  remove  the  pellicle  which  forms  from  time 
to  time  upon  the  surface.  Being  now  allowed  to  stand,  a  copious 
deposit  of  crystalline  needles  is  obtained.  These,  when  sepa- 
rated from  the  mother-liquor  by  a  filter,  washed  with  alcohol 
and  cold  water,  and  then  purified  by  crystallization  from  hot 
water,  are  pure  creatine. 

The  crystals  of  creatine  are  transparent,  very  brilliant,  belong 
to  the  clinorhombic  system,  and  con- 
tain two  atoms  of  water.  It  is  bitter, 
pungent,  and  irritates  the  pharynx 
when  swallowed.  At  212°  it  loses  its 
water,  and  at  a  higher  heat  is  decom- 
posed. It  dissolves  in  74.4  parts  of 
cold  water,  but  in  much  less  boiling 
water.  It  requires  9410  parts  of  alco- 
hol to  dissolve  it,  and  is  insoluble  in 
ether.  Boiled  with  baryta  water,  it  is 
decomposed  into  ammonia  and  car- 
bonic acid,  or  into  urea  and  sarcosine. 
The  formula  of  the  anhydrous  sub- 
and  its  atomic  weight  is  1637.5. 


Creatine,  prepared  from  beef  and 
crystallized  from  hot  water. 


Stance  is  C8HQN3O4, 


NITROGENOUS  BASIC  BODIES.  55 

Creatine  is  a  constant  constituent  of  muscular  flesh,  though 
found  in  very  small  quantity.  The  proportion  varies  in  differ- 
ent animals.  In  man,  Schlossberger  estimates  it  at  0.067^  of 
muscle.  It  is  not  to  be  found  in  the  substance  of  the  brain,  the 
liver,  or  the  kidneys.  It  is  also  found  very  constantly  in  the 
urine. 

The  following  is  Liebig's  method  of  procuring  it  from  this 
fluid.  The  urine  is  treated  with  lime-water  and  chloride  of  cal- 
cium, filtered,  evaporated,  and  crystallized  to  remove  the  salts. 
The  mother-liquor  is  decomposed  with  one-twenty-fourth  of  its 
weight  of  a  syrupy  solution  of  chloride  of  zinc.  After  some 
days,  roundish  granules  of  a  compound  of  chloride  of  zinc  with 
creatinine,  mixed  with  some  creatine,  separate.  These  granules 
are  dissolved  in  boiling  water,  and  the  solution  treated  with 
hydrated  oxide  of  lead  till  the  reaction  becomes  alkaline.  The 
filtered  fluid  is  treated  with  animal  charcoal  and  evaporated  to 
dryness.  Boiling  alcohol  dissolves  the  creatine  and  leaves  the 
creatinine. 

It  was  at  one  time  supposed  that  creatine  was  the  result  of  a 
progressive  metamorphosis,  and,  therefore,  a  nutritive  substance. 
Liebig's  researches,  however,  have  clearly  proved  it  to  be  a  pro- 
duct of  excretion.  It  is  probably  an  intermediate  stage  between 
muscular  tissue  and  urea. 

CREATININE. 

The  method  of  obtaining  this  body  from  urine  has  already 
been  mentioned.  It  is  more  easily  obtained  by  mixing  creatine 
with  hydrochloric  acid,  evaporating  till  all  excess  of  acid  has 
passed  off,  and  digesting  with  hydrated  oxide  of  lead,  to  decom- 
pose the  hydrochlorate  thus  formed. 

It  forms  colorless,  very  glistening  crystals  belonging  to  the 
monoclinometric  system;  has  a  caustic,  burning  taste;  is  soluble 
in  11.5  parts  of  water  at  ordinary  temperatures,  in  less  hot 
water,  in  100  parts  of  cold  spirit  of  wine,  and  very  freely  in  hot 
alcohol.  It  is  slightly  soluble  in  ether.  It  is  precipitated  in 
crystals  by  nitrate  of  silver,  corrosive  sublimate,  and  chloride  of 
zinc.  Bichloride  of  platinum  gives  no  precipitate  in  a  dilute 
solution. 


56 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


According  to  Liebig,  its  formula  is  CgH^NjOj,  and  its  atomic 

weight,  1412.5. 
Fig.  3.  Liebig  has  only  found  this 

substance  in  flesh  and  urine. 
Its  proportion  is  unknown, 
but  there  is  less  of  it  than 
of  creatine.  Scherer's  re- 
searches have  rendered  it 
probable  that  the  liquor  am- 
nii  contains  creatinine. 

It  is  probably  formed  from 

creatine.      These  substances 

are  found  in  inverse  ratio  in 

muscles  and  urine  ;  and  the  latter  fluid,  when  putrid,  yields 

no  creatine,  but  only  creatinine.      It  is,  therefore,  apparently, 

another  step  in  the  regressive  metamorphosis. 


Creatinine. 


TYROSINE. 

When  cheese,  freed  from  butter,  is  fused  with  hydrate  of 
potash  till  hydrogen  is  given  off,  or  till  the  brown  tint  has  passed 
into  a  yellow,  tyrosine  is  formed  at  the  expense  of  the  casein. 
On  dissolving  in  hot  water  and  treating  with  acetic  acid,  the 
tyrosine  separates  in  needles,  which  are  purified  by  solution  in 
potash  water  and  a  second  acidulation  with  acetic  acid. 

It  forms  silky,  glistening,  dazzlingly  white  needles,  of  diffi- 
cult solubility  in  water,  and  altogether  insoluble  in  alcohol  and 
ether.  It  dissolves  readily  in  alkalies,  and  combines  with  acids, 
except  the  acetic. 

Liebig's  formula  is  CigllgNOj,  but  he  thinks  it  needs  revision. 

Tyrosine  is  formed  during  the  putrefaction  of  albumen,  fibrin, 
and  casein. 

LEUCINE. 

The  mother-liquor,  remaining  after  the  separation  of  tyrosine 
from  casein  fused  with  potash,  contains  leucine,  which  crystal- 
lizes from  it,  and  is  easily  purified  by  recrystallization  from 
alcohol. 


NITROGENOUS  BASIC  BODIES. 


57 


Leucine. 


It  occurs  in  glistening,  colorless  leaves,  wliicli  cranch  beneath 
the   teeth,    and   convey  to 

them   the    sensation    of    a  ^ig-  4. 

fatty  matter.  It  is  taste- 
less and  inodorous  ;  fuses 
above  212° ;  sublimes  un- 
changed when  carefully 
heated  to  338° ;  is  solu- 
ble in  27.7  parts  of  water 
at  63°,  in  625  parts  of  al- 
cohol of  0.828,  and  in  much 
smaller  quantities  of  hot 
water  and  alcohol.      It   is 

insoluble  in  ether.  Proto-nitrate  of  mercury  is  the  only  reagent 
which  precipitates  it  from  its  watery  solution.  It  dissolves 
more  readily  in  ammoniacal  than  in  pure  water.  It  dissolves 
unchanged  in  cold  hydrochloric  and  sulphuric  acids,  and  the 
solution  may  be  warmed  without  the  occurrence  of  decomposi- 
tion ;  it  also  dissolves  unchanged  in  cold  nitric  acid,  but  on 
boiling  it  is  volatilized.  When  oxidated,  nitrogen  is  given  off 
and  leucic  acid  (CjjHjjOjHO)  is  formed.  Fused  with  hydrated 
potash,  carbonic  acid,  hydrogen,  and  valerianate  of  ammonia  are 
simultaneously  formed. 

Mulder's  formula  is  CjjHjjNO^.  Recent  investigations,  how- 
ever, by  a  number  of  observers,  have  established  the  formula 
Ci^HjjNO^.     Its  atomic  weight  is  1637.5. 

Leucine  combines  with  acids  to  form  beautifully  crystallizable 
salts. 

It  may  be  obtained  from  gelatin,  as  well  as  from  albuminous 
substances,  by  fusing  with  hydrated  potash.  It  is  also  procured 
from  flesh  by  warming  it  with  concentrated  sulphuric  acid. 


SARCOSINE. 


This  substance  Is  obtained  as  a  result  of  the  decomposition  of 
creatine,  and  does  not  occur  ready  formed  in  the  animal  body. 
A  boiling,  saturated  solution  of  one  part  of  creatine  is  digested 
with  ten  parts  of  pure,  crystallized,  caustic  baryta ;  and,  after 


58 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


ammonia  ceases  to  be  given  off,  the  carbonate  of  baryta  is 
filtered  oif,  and  sarcosine  allowed  to  crystallize  from  the  liquid. 

It  occurs  in  broad,  colorless,  transparent  plates  or  right 
rhombic  prisms,  acuminated  on  the  ends,  melting  at  212°,  and 
subliming  unchanged  at  a  higher  temperature.  It  is  very  solu- 
ble in  water,  sparingly  so  in  alcohol,  and  not  at  all  in  ether.  It 
has  a  sharp,  sweetish,  faintly  metallic  taste,  and  with  salts  of 
copper  gives  the  same  fine  blue  tint  as  ammonia. 

Its  formula,  according  to  Liebig,  is  CgH^NOj,  its  atomic 
weight  1012.5. 


GLYCINE. 

This  substance,  also  known  as  sugar  of  gelatin  and  gli/cocoU, 
is  obtained  as  a  result  of  the  decomposition  of  gelatin  by  the 
concentrated  mineral  acids  or  the  caustic  alkalies.  If  gelatin 
be  boiled  with  a  strong  solution  of  potash,  it  is  entirely  resolved 
into  four  parts  of  glycine  and  one  of  leucine.  The  fluid,  neu- 
tralized with  sulphuric  acid,  is  evaporated  to  dryness,  and  the 

residue   extracted  with   alcohol, 
^ig-  ^-  which   dissolves  both  alkaloids. 

The  glycine,  being  less  soluble 
than  the  leucine,  crystallizes  first, 
and  is  purified  by  recrystalliza- 
tion  and  treatment  with  animal 
/  /  ^  /  charcoal. 
/^^^^    \^  >K^^!'^  f]^  ^^®  crystals  are  colorless,  rhom- 

'^^^  bic  prisms,  cranching  between 
the  teeth,  inodorous,  sweet,  but 
not  so  much  so  as  cane-sugar. 
They  dissolve  in  4.3  parts  of 
cold  water,  and  with  more  diffi- 
culty in  cold,  but  more  easily  in  hot  alcohol.  They  are  inso- 
luble in  ether,  and  have  no  efi"ect  on  vegetable  colors.  Sulphate 
of  copper  and  potash  form  with  it  a  blue  solution,  which,  Avhen 
heated,  lets  fall  no  suboxide  of  copper.  Boiled  with  hydrated 
baryta  or  oxide  of  lead,  it  gives  off  ammonia,  and  assumes  a 
fiery-red  tint,  which  passes  ofi"  on  the  prolonged  application  of 
heat. 


Glycine. 


NITROGENOUS  BASIC  BODIES. 


69 


The  formula  of  glycine  dried  at  212°  is  C4H3NO3,  its  atomic 
vreiglit,  937.5. 

Glycine  forms  crystallizable  compounds  with  acids,  salts,  and 
bases. 

It  has  not  yet  been  found  in  an  isolated  state  in  the  body,  but 
it  is  supposed  to  exist  there,  in  combination  with  animal  acids, 
from  which  it  is  separated  by  the  process  already  described. 
Taken  into  the  system,  it  increases  the  amount  of  urea  and  uric 
acid,  but  is  not  found  unchanged  in  the  urine. 


UREA. 

This  substance  exists  in  the  urine,  and  may  be  obtained  from 
it  by  evaporating  to  dryness,  extracting  the  residue  with  alco- 
hol, precipitating  the  urea  as  a  nitrate  by  means  of  nitric  acid, 
decomposing  the  salt  with  carbonate  of  lead  or  baryta,  sepa- 
rating these  by  crystallization  or  by  hydrosulphuric  acid,  evapo- 
rating and  crystallizing. 

It  is  also  obtained  by  mixing  twenty-eight  parts  of  anhydrous 
ferrocyanide  of  potassium  with  fourteen  parts  of  well-dried, 
good  peroxide  of  manganese,  and  heating  to  redness.  It  is  then 
extracted  with  cold  water  and  mixed  with  twenty  and  a  half 
parts  of  dry  sulphate  of  ammonia.  Sulphate  of  potash  separates, 
and  the  cyanate  of  ammonia,  now  converted  into  urea,  remains 
in  solution. 

It  crystallizes  in  white,  silky,  ~" 

glistening  needles,  or  flat,  co- 
lorless, four-sided  prisms,  full 
of  cavities,  and  apparently 
made  up  of  numerous  parallel, 
crystalline  lamellae ;  the  ends 
being  terminated  by  one  or  two 
oblique  surfaces.  It  is  devoid 
of  smell,  has  a  cooling,  saltish 
taste,  and  is  unajBfected  by  ex- 
posure to  the  atmosphere.  It 
dissolves  readily  in  its  own 
weight  of  water,  with  evolution  of  heat;   and  in  every  pro- 


60  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

portion  of  hot  water.  It  is  soluble  in  four  or  five  parts  of  cold 
and  two  parts  of  hot  alcohol,  but  insoluble  in  pure  ether  and 
ethereal  oil.  It  has  no  action  on  vegetable  colors.  Its  conceji- 
trated  aqueous  solution  is  not  changed  by  boiling  or  by  long 
keeping,  but  a  dilute  solution  suffers  change.  At  about  250°  it 
fuses  without  change  ;  a  little  above  that  temperature  it  begins 
to  develop  ammonia,  and  is  converted  into  cyanuric  acid,  which 
passes,  by  being  rapidly  heated,  into  cyanic  acid.  AVhen  kept 
in  fusion  some  time  at  from  300°  to  340°,  biuret  is  formed  in 
addition  to  the  above-named  compounds. 

Urea  combines  only  with  certain  acids  and  with  but  a  few 
bases.  Neither  the  metallic  salts,  tannic  acid,  nor  any  other 
reagent  can  precipitate  it  from  its  solutions.  Nitrous  acid 
decomposes  it  into  nitrogen,  water,  and  carbonic  acid ;  chlorine, 
into  nitrogen,  carbonic,  and  hydrochloric  acids.  Boiled  either 
with  strong  mineral  acids  or  Avith  caustic  alkalies,  it  takes  up 
two  atoms  of  water,  and  is  decomposed  into  ammonia  and  car- 
bonic acid.  The  same  change  takes  place,  when  putrefying  or 
putrifiable  organic  matter  is  introduced  into  solutions  of  urea. 

The  formula  of  urea  is  C2H4N2O2,  its  atomic  weight  750. 
Dumas  thought  it  an  amide  of  carbonic  acid ;  Berzelius,  an 
ammonia  conjugated  with  a  nitrogenous  body  which  he  calls 
urenoxide;  an  idea  which  Lehmann  thinks  is  fully  borne  out  by 
its  reactions. 

There  are  but  three  salts  of  urea,  the  hydrochlorate,  the 
nitrate,  and  the  oxalate. 

The  hydroclilorate  is  white  and  hard,  crystallizing  in  plates 
which  deliquesce,  and  are  gradually  decomposed  by  the  action  of 
the  atmosphere. 

The  nitrate  separates,  on  mixing  nitric  acid  in  excess  with  a 
concentrated  solution  of  urea,  in  large,  nacreous,  shining  scales, 
or  in  small,  glistening,  white  plates.  It  is  unalterable  by  the 
atmosphere,  is  acid  in  its  taste,  more  soluble  in  pure  water  than 
in  water  containing  nitric  acid,  soluble  in  alcohol,  with  great 
depression  of  temperature.  It  rendens  litmus,  decrepitates  on 
being  heated,  but  when  its  temperature  is  slowly  raised  to  284° 
it  is  decomposed  into  carbonic  acid,  nitrous  acid,  urea,  and  nitrate 


NITROGENOUS  BASIC  BODIES. 


61 


of  ammonia.     From  a  solution  not  too  dilute,  oxalic  acid  preci- 
pitates oxalate  of  urea. 

Oxalate  of  urea  may  be  obtained  by  direct  union  of  the  two 
elements.  It  forms  long  thin  plates  or  prisms,  and  under  the 
microscope  usually  appears  in  hexagonal  plates,  similar  to  those 
of  nitrate  of  urea,  intermingled  with  four-sided  prisms. 

In  testing  albuminous  fluids  for  urea,  it  is  first  necessary  tho- 
roughly to  coagulate  the  protein  compounds,  by  acidulating  with 
acetic  acid  before  boiling.  The  remaining  fluid  is  extracted 
•with  cold  alcohol,  and  rapidly  evaporated  till  the  chloride  of 
sodium  crystallizes  out  as  completely  as  possible.  Then,  on 
bringing  a  drop  of  the  mother- water  in  contact  with  nitric  acid 
under  the  microscope,  rhombic  octahedra  and  hexagonal  tablets 
make  their  appearance.  If  the  angles  of  these  crystals  are 
found  to  measure  82°,  the  presence  of  urea  is  rendered  certain. 

Mitscherlich  estimated  the  quantity  of  this  salt  by  converting 
it  into  nitrate  of  urea,  and 
■weighing   as   such.     This  Fig-  7. 

is  subject  to  many  errors. 
To  obtain  a  tolerably  cor- 
rect result,  it  is  necessary 
to  use  an  excess  of  nitric 
acid,  to  lower  the  tempe- 
rature artificially,  and  al- 
low the  precipitate  to  cool 
some  time  before  filtering, 
to  rinse  the  salt  with  cold 
nitric  acid,  to  press  it,  and 
to  dry  in  a  temperature 
not  exceeding  230°.  The 
method  by  sulphuric  acid 
is  much  more  exact.  The 
amount  of  potash  and  am- 
monia in  the  sample  of  urine  having  first  been  determined,  a 
second  specimen  is  treated  with  sulphuric  acid,  and  heated  to 
360°  or  390°  as  long  as  any  efi'ervescence  occurs ;  the  fluid  is 
then  filtered,  and  the  ammonia  estimated  as  ammonio-chloride  of 
platinum.     From  this  it  is  easy  to  calculate  the  amount  of  urea. 


Nitrate  of  Urea. 


6'2  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

Millon's  method  is  based  upon  the  fact  that  nitrous  acid  de- 
composes urea  into  nitrogen  and  carbonic  acid.  To  effect  this, 
nitrite  of  suboxide  of  mercury  is  dissolved  in  nitric  acid,  and 
added  to  a  weighed  portion  of  urine.  When  this  is  warmed, 
nitrogen  and  carbonic  acid  escape,  and  the  latter  being  fixed  in 
a  potash-bulb,  is  weighed.  It  must  always  be  remembered  that 
free  carbonic  acid  has  been  shown  to  exist  in  the  urine. 

Bunsen  has  proposed  a  method  based  on  the  fact  that,  in  closed 
vessels,  solutions  of  urea  undergo  decomposition  at  a  temperature 
from  250°  to  460°.  The  carbonic  acid  thus  formed  is  com- 
bined with  baryta,  weighed,  and  the  urea  calculated  from  it. 

Phjsiological  Relations. — Urea,  being  one  of  the  chief  pro- 
ducts of  renal  excretion,  occurs  chiefly  in  the  urine.  Its  pro- 
portion to  the  entire  secretion  varies  greatly,  in  consequence  of 
the  variable  amount  of  water  contained  in  urine.  As  a  general 
thing,  however,  it  constitutes  from  2.5  to  3.2g  of  the  entire 
secretion.  Its  ratio  to  the  other  solid  constituents  is  about 
9  :  11  or  7  :  9 ;  and  a  healthy  man,  in  twenty-four  hours,  excretes 
from  340  to  416  grains. 

Lehmann  has  shown  that  the  excretion  of  urine  depends  very 
much  on  the  nature  of  the  diet.  Thus,  his  own  natural  evacua- 
tion of  urea,  with  a  mixed  diet,  being  32.5  grammes  (401.6 
grains);  he  excreted,  on  a  purely  animal  diet,  53.2  grammes; 
on  a  purely  vegetable  one,  22.5  grammes;  and  on  a  non-nitro- 
genous diet,  15.4  grammes.  This  excretion  goes  on  even  while 
fasting.  Lassaigne  found  urea  in  the  urine  of  a  madman  who 
had  fasted  fourteen  days,  and  Lehmann  found  1^  of  it  in  his 
own  urine  after  living  three  days  on  non-nitrogenous  food. 

Strong  muscular  exercise  increases  its  quantity.  Lehmann 
found  his  own  urea  increased  from  32  to  37  grammes  by  it. 
Women,  according  to  Becquerel,  secrete  less  than  men  in  the 
proportion  of  15.6  to  17.6. 

Urea  is  found  in  the  blood,  especially  in  Bright's  disease. 
It  has  also  been  detected  in  milk,  bile,  saliva,  and  dropsical 
effusions. 

The  difficulty  of  detecting  urea  in  the  blood  led  the  old  phy- 
siologists to  suppose  that  it  was  formed  in  the  kidneys,  and  that 
when  it  occurred  in  the  blood  it  was  in  consequence  of  resorp- 


NITROGENOUS  BASIC  BODIES.  63 

tion.  It  was  found,  however,  that  it  existed  in  large  quantities 
when  the  kidneys  were  extirpated,  and  that  the  imperfection  of 
our  analytical  methods  is  so  great  that  it  is  impossible  to  detect 
quite  a  large  quantity  of  this  substance  dissolved  in  blood.  If, 
then,  we  consider  that  it  is  swept  out  by  the  kidneys  as  fast  as 
it  is  formed,  we  shall  not  be  surprised  at  the  impossibility  of 
detecting  it,  at  present,  in  healthy  blood. 

Supposing  it  to  exist  in  blood,  the  next  question  is,  whether 
it  is  formed  there  or  in  the  muscles.  Liebig,  in  his  extensive 
researches  on  muscular  fluids,  could  detect  no  urea  in  them, 
though  he  found  substances  from  which  it  could  be  artificially 
produced.  It  is  therefore  probable  that  it  is  formed  in  the  blood 
from  substances  taken  up  from  the  muscles,  in  consequence  of 
the  action  of  the  free  oxygen  and  alkali  contained  in  that  fluid 
upon  them.  Among  these,  creatine  and  inosic  acid  probably 
play  a  very  important  part.  The  excess  of  nitrogenous  food  is 
also  most  likely  converted  into  urea  in  the  blood. 

XANTHINE. 

When  carbonic  acid  is  passed  through  the  potash  solution  of 
certain  urinary  calculi,  there  falls  a  white  powder,  which  is  nei- 
ther crystalline  nor  gelatinous.  When  dried,  it  forms  pale  yel- 
lowish, hard  masses,  which,  when  rubbed,  assume  a  waxy  bright- 
ness. It  is  very  slightly  soluble  in  water,  insoluble  in  alcohol 
and  ether,  and  when  heated  decomposes  without  fusion.  It  dis- 
solves in  ammonia ;  but,  on  evaporation,  loses  the  greater  part 
of  the  alkali,  and  separates  as  a  yellowish,  foliaceous  mass.  It 
dissolves  freely  in  the  caustic  alkalies,  from  which  carbonic  acid 
separates  it.  It  dissolves  in  nitric  acid  without  development  of 
gas,  and  in  sulphuric  acid,  to  which  it  communicates  a  yellow 
color.  It  is  nearly  insoluble  in  hydrochloric  and  oxalic  acids, 
and  forms  no  definite  compounds  with  acids,  alkalies,  or  salts. 

Its  formula  has  been  calculated  at  C^H^N^O^.  It  has  been 
regarded  as  uric  acid  in  a  lower  state  of  oxidation,  but  nothing 
definite  is  known  about  it. 

It  has  been  rarely  found  in  the  human  body,  and  then  in 
animal  calculi.     Scherer  has  discovered  a  substance  which  he 


64 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


calls  hypoxanthine,  because  it  contains  one  equivalent  of  oxygen 
less  than  xanthine. 

GUANINE. 

This  substance,  as  its  name  implies,  is  obtained  from  guano. 
This  excrement  is  digested  in  diluted  milk  of  lime,  till  the  fluid 
no  longer  appears  brown,  but  greenish  yellow  when  boiled.  It 
is  then  filtered,  and  treated  with  hydrochloric  acid.  In  a  few 
hours  it  separates  with  a  little  uric  acid.  It  is  purified  by  solu- 
tion in  hydrochloric  acid,  crystallization,  and  separation  from 
the  acid  by  ammonia. 

It  is  a  yellowish-white  crystalline  powder,  without  taste  or 
smell;  insoluble  in  water,  alcohol,  or  ether,  soluble  in  hydro- 
chloric acid  and  caustic  soda.  It  forms  unstable  salts  w^ith 
water. 

It  consists  of  CJ0H3NJO2,  and  its  atomic  weight  is  1887.5. 

It  is  found  in  the  excrements  of  sea-fowl  and  of  spiders.  It 
is  probably  the  xanthine  which  Strahl  and  Lieberkiihn  found  in 
human  urine. 


Fig.  8. 


ALLANTOINE. 

When  the  allantoic  fluid  of  a  foetal  calf  or  the  urine  of  the 

young  animal  is  evaporated,  below 
the  boiling  point,  to  a  thin  syrup, 
crystals  of  allantoine  mixed  with 
phosphate  and  urate  of  magnesia  are 
formed.  The  urate  of  magnesia  is 
washed  away  from  the  crystals,  and 
the  two  remaining  substances  sepa- 
rated with  hot  water,  which  dissolves 
the  allantoine,  leaving  the  raagnesian 
salt.  Treatment  with  animal  char- 
coal and  recrystallization  purify  it. 

It  occurs  in  the  form  of  colorless, 
hard  prisms,  with  a  strong  vitreous 
lustre ;    is  tasteless  and  inodorous ; 
crystallizes    from    its    hot    alcoholic 
solution;  is  insoluble  in  ether;  dissolves  in  160  parts  of  cold 


NITROGENOUS  BASIC  BODIES. 


65 


water  and  more  easily  in  hot  water.  It  is  unalterable  in  the 
air;  does  not  redden  litmus;  and,  when  heated,  chars  without 
fusing.  It  dissolves,  with  the  aid  of  warmth,  in  the  caustic 
alkalies  and  their  carbonates,  but  crystallizes  from  them  un- 
changed when  they  cool.  Concentrated  caustic  alkalies  decom- 
pose it  into  oxalic  acid  and  ammonia. 

Its  formula  is  CgH^N^O^+HO  ;  its  atomic  weight,  1862.5. 

It  is  found  only  in  the  allantoic  fluid  of  the  cow's  foetus  and 
in  the  urine  of  the  newly-born  animal.  In  the  urine  of  suck- 
ing calves,  it  occurs  together  with  uric  acid  and  urea,  but  with- 
out hippuric  acid,  whence  it  has  been  suggested  that  hippuric 
acid  and  allantoine  substitute  one  another  in  the  economy. 


Fis.  9. 


CYSTINE. 

When  certain  urinary  calculi  are  dissolved  in  potash,  the 
addition  of  acetic  acid  separates  cystine  from  them.  The  same 
substance  is  obtained  by  dissolving  the  calculi  in  ammonia,  and 
allowing  them  to  crystallize  out  by  spontaneous  evaporation. 

This  body  occurs  in  colorless,  transparent,  hexagonal  plates 
or  prisms.  It  is  tasteless,  inodorous,  insoluble  in  water  or  alco- 
hol. It  does  not  fuse,  but  burns 
with  a  bluish-green  flame  and  a 
peculiar  acid  odor. 

Its  formula  is  CgHgNSjO^;  its 
atomic  weight,  1336.  It  com- 
bines with  a  few  acids  and  some 
salts. 

It  is  a  substance  of  rare  oc- 
currence, having  been  found  in 
but  few  urinary  calculi.  Gold- 
ing  Bird  and  Mandl  have  found 
it  dissolved  in  the  urine,  and  it  occurs  in  urinary  sediments 
mixed  with  urate  of  soda.  It  is  the  only  urinary  body  which 
contains  sulphur,  and  that  metalloid  exists  in  larger  proportion 
in  it  than  in  any  other  organic  body,  not  excepting  taurine.  The 
percentage  of  sulphur  in  cystine  is  26,  in  taurine  25.  Hence, 
5 


Cystine 


66 


PKINCIPLES  OF  ANIMAL  CHEMISTRY. 


Lehmann   observes,  the  rational   physician   should  direct  his 
attention  to  the  liver  when  cystine  is  found  in  the  urine. 


TAURINE. 

This  substance,  formerly  called  biliary  asparagin,  is  obtained 
from  the  alcoholic  solution  of  ox-gall  by  mixing  it  with  hydro- 
chloric  acid,  boiling  it   till  no  more 
I'ig- 10-  choloidic  acid  is  formed,  filtering,  eva- 

porating till  the   chloride  of  sodium 
crystallizes  out,  and  then  treating  the 
acid  mother-liquor  with  boiling  alcohol. 
(  \     i  <^  Taurine  separates  in  needles  as  the  mix- 

V*    I    /^--^^h       ^^^'^  cools,  and  is  purified  by  recrys- 
tallization  from  water. 

It  crystallizes  in  characteristic  hexa- 
gonal prisms,  with  four  and  six-sided 
sharp  extremities,  is  hard,  craunches 
beneath  the  teeth ;  is  soluble  in  15.5 
Taurine.  parts  of  watcr,  and  573  of  spirit  of 

wine. 
Its  formula  is  C^H^NSjOg.     Its  atomic  weight  has  not  been 
determined. 

It  is  recognized  by  the  form  of  its  crystals,  by  its  property  of 
developing  sulphurous  acid  when  heated  with  free  access  of  air, 
and  by  its  not  blackening  when  boiled  with  caustic  potash,  but 
developing  ammonia,  and  leaving  nothing  in  solution  but  sul- 
phurous and  acetic  acids. 

Taurine  has  never  been  found  isolated  in  the  healthy  organism, 
but  is  supposed  to  be  preformed  in  the  bile,  and  then  conjugated 
with  cholic  acid.  Of  its  origin,  little  is  known;  of  its  use,  no- 
thing. It  has  been  supposed  that  it  is  formed  mainly  from  the 
sulphur  of  the  albuminous  food  during  its  nutritive  metamor- 
phosis. 


NITROGENOUS  ACIDS. 


67 


CHAPTER    VI. 


NITROGENOUS  ACIDS. 


These  have  been  described  by  Lehmann  as  conjugated  acids, 
that  is,  as  acids  which  are  combined  with  mere  basic  substances 
without  losing  their  saturating  power.  The  organic  substance, 
combined  with  the  acid,  however,  materially  alters  its  proper- 
ties, while  it  does  not  affect  its  acidity. 

Carhazotic  or  j02cr?c  acid  is  a  yellow,  crystalline  substance, 
the  result  of  the  action  of  nitric  acid  upon  many  vegetable  and 
animal  substances.  It  is  usually  obtained  by  boiling  indigo  in 
nitric  acid.  It  has  been  suggested  as  a  test  for  potash,  but  the 
author's  experience  with  it  has  been  anything  but  satisfactory. 

Its  formula  is  CjjHgNjOjj+HO;  its  atomic  weight,  2750;  its 
saturating  capacity,  3.636. 


HIPPURIC  ACID. 

Hippuric  or  uro-henzoic  acid  is  a  constant  constituent  of 
horse's  urine.  The  fresh  urine  of  the  horse  is  evaporated  to 
one-eighth  of  its  volume,  and  then  treated  with  hydrochloric  acid. 
On  cooling,  hippuric  acid,  contaminated  with  much  coloring 
matter,  separates.  To  purify  it,  it  is  boiled  with  milk  of  lime, 
mixed  with  alum,  and  the  alumina 
precipitated  with  bicarbonate  of 
soda.  The  hippurate  of  soda  is 
decomposed  with  hydrochloric  acid, 
the  precipitate  boiled  with  animal 
charcoal,  and  filtered  while  hot.  The 
acid  now  separates  colorless,  as  the 
solution  cools. 

It  crystallizes  in  minute  spangles 
or  larger,  obliquely-striated,  four- 
sided  prisms.     Its  elementary  form  „.      .     ., 

■T  J  Hippuric  acid. 


68  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

is  a  vertical  rhombic  prism.  It  is  bitter,  inodorous,  soluble  in  400 
parts  of  cold  water,  very  freely  in  hot  water  and  in  alcohol,  but 
insoluble  in  ether.  Gently  heated,  it  fuses ;  with  a  stronger 
heat,  a  crystalline  sublimate  of  benzoic  acid  and  benzoate  of 
ammonia  is  obtained,  while  a  few  oily  drops  appear,  which  emit 
an  odor  of  cumarin,  the  oil  of  Tonka  bean.  A  higher  heat 
reduces  the  acid  to  a  porous  coal,  with  the  development  of  a 
very  strong  odor  of  hydrocyanic  acid.  In  fermenting  or  putre- 
fying fluids,  it  is  decomposed  into  benzoic  acid  and  unknown 
products. 

Its  formula  is  CigHgNOj+HO,  its  atomic  weight  2125,  and 
its  saturating  capacity  4.706.  Its  constitution  has  been  vari- 
ously expounded  by  different  chemists,  and  nothing  definite  has 
yet  been  determined.  It  has  been  supposed  to  be  glycine  con- 
jugated with  benzoic  acid. 

Benzoic  acid  is  the  only  one  with  which  it  is  likely  to  be  con- 
founded, but  it  may  be  distinguished  from  it  by  its  method  of 
crystallization.  Hippuric  acid  crystallizes  from  hot  solutions  in 
prisms,  benzoic  acid  in  scales. 

Liebig  has  shown  that  this  acid  exists  in  small  quantity  in 
healthy  human  urine.  In  various  forms  of  disease,  it  is  also 
found.  In  febrile  urine,  it  is  often  present.  It  occurs  also  in 
diabetes,  and  has  been  found  in  the  urine  of  drunkards  and  of 
patients  suffering  with  chorea.  It  is  rapidly  formed  after  the 
ingestion  of  benzoic  acid.  Its  origin  is  unknown,  but  it  probably 
comes  from  the  debris  of  the  albuminous  tissues. 

URIC  ACID. 

The  best  process  for  obtaining  uric  acid  is  that  devised  by 
Bensch.  It  consists  in  boiling  the  excrements  of  serpents,  or  of 
birds,  or  uric  acid  calculi  in  a  solution  of  one  part  of  hydrated 
potash  in  twenty  parts  of  water  till  no  more  ammoniacal  fumes 
are  evolved.  Carbonic  acid  is  passed  through  the  solution  till 
the  alkaline  reaction  nearly  disappears.  The  precipitated  urate 
of  potash  is  washed  in  cold  water  till  it  begins  to  dissolve  ;  it  is 
then  dissolved  in  a  solution  of  potash,  warmed,  and  treated  with 
hydrochloric  acid,  when  pure  uric  acid  precipitates. 


NITROGENOUS  ACIDS. 


69 


It  occurs  either  in  a  glittering  white  powder  or  in  very  minute 
scales,  which,  under  the  microscope,  are  seen  to  be  made  up  of 
irregular  plates.  It  is  soluble  in  1800  parts  of  hot  and  14,000 
parts  of  cold  water,  insoluble  in  alcohol  and  ether,  and  does  not 
redden  litmus.  It  dissolves  readily  in  carbonates  and  other 
alkaline  salts.  It  is  disengaged  from  its  combinations  by  acetic 
and  other  acids,  and  forms  a  gelatinous  mass,  changing  into 
small  glistening  plates. 

It  is  one  of  the  weakest  of  the  acids.  It  does  not  disengage 
carbonic  acid  from  carbonate  of  potash,  but  gives  rise  to  the 
formation  of  urate  and  bicarbonate  of  potash  if  added  in  suffi- 
cient quantity.  In  a  concentrated 
solution,  the  urate  of  potash  remains 
undissolved. 

By  dry  distillation  it  is  converted 
into  urea,  cyanic  acid,  cyamelide,  hy- 
drocyanic acid,  and  carbonate  of  am- 
monia, and  leaves  a  brownish-black 
coal,  rich  in  nitrogen.  Fused  with 
hydrated  potash,  carbonate  and  cya- 
nate  of  potash  with  cyanide  of  potas- 
sium are  formed.  In  nitric  acid  it 
dissolves,  giving  off  equal  volumes  of 
nitrogen  and  carbonic  acid.  On  eva- 
porating this  solution  to  dryness,  a 

red  amorphous  residue  (murexide)  remains,  which,  exposed  to  the 
vapor  of  ammonia,  assumes  a  very  beautiful  purple  tint ;  and  is 
rendered  violet-colored  by  treatment  with  caustic  potash. 

Its  formula  is  C5HN2O2-I-HO,  its  atomic  weight  937.5,  and 
its  saturating  capacity  10.656.  Several  theories  have  been 
advanced  to  explain  its  constitution,  but  all  have  fallen  to  the 
ground. 

It  forms  soluble  and  neutral  salts  with  the  fixed  alkalies  ;  with 
ammonia  and  other  bases,  it  forms  only  acid  and  insoluble  com- 
pounds. 

The  products  of  the  metamorphosis  of  uric  acid  are  very  nume- 
rous, and  have  been  carefully  studied,  but  as  yet  they  possess 
little  or  no  physiological  interest.     It  would  take  up  too  much 


Uric  acid. 


70  PKINCIPLES  OF  ANIMAL  CHEMISTRY. 

space  to  recount  all  these  bodies,  and  the  reader  is  therefore 
referred  to  Golding  Bird's  Urinary  Deposits^  Simon's  Animal 
Chemistry,  and  the  excellent  work  of  Lehmann,  already  so  often 
quoted  and  so  frequently  referred  to. 

Uric  acid  is  easily  recognized  by  the  murexide  test,  that  is, 
by  evaporating  to  dryness,  and  adding  caustic  potash,  when  the 
red  amorphous  residue  will  assume  a  fine  violet  color.  The 
microscope  also  readily  detects  this  substance,  since  its  crystal- 
line forms,  though  various,  are  so  very  remarkable. 

The  quantitative  estimation  of  it  in  the  urine  is  easily  made  by 
dissolving  out  the  earths  with  hydrochloric  acid  from  the  residue 
left  after  extracting  evaporated  urine  with  alcohol.  Uric  acid 
and  mucus  remain.  The  first  is  taken  up  by  dilute  solution  of 
potash,  and  the  urate  of  potash  decomposed  by  means  of  acetic 
acid.  In  determining  its  presence  in  albuminous  fluids,  it  is 
necessary  to  evaporate  to  dryness,  extract  with  alcohol  and 
water,  and  seek  for  the  acid  in  the  watery  solution. 

Uric  acid  is  always  found  in  the  urine  of  healthy  men,  in  the 
proportion  of  about  one  part  in  every  thousand  of  urine.  The 
nature  of  the  food  exerts  very  little  influence  over  the  propor- 
tion of  this  ingredient.  It  is  a  little  increased  by  an  animal  and 
slightly  diminished  by  a  vegetable  diet. 

It  has  been  generally  stated  that  the  increased  activity  of  the 
skin  in  summer  was  unfavorable  to  the  discharge  of  uric  acid  by 
the  kidneys.  Lehmann,  however,  declares  that  the  only  result 
he  was  able  to  arrive  at,  after  a  number  of  experiments,  was, 
that  the  amount  of  water  in  the  urine  was  increased  in  winter 
and  diminished  in  summer,  but  that  the  solid  constituents,  espe- 
cially the  acid  under  consideration,  was  neither  increased  nor 
diminished. 

In  disturbed  or  imperfect  digestion,  the  amount  of  this  sub- 
stance is  usually  very  much  increased.  In  fever,  also,  there  is 
more  uric  acid  formed  than  in  health.  The  deposit  which  almost 
always  clouds  the  acid  urine  of  febrile  patients  consists  of  urate 
of  soda.  Its  occurrence  in  acid  urine  may  be  easily  explained 
by  its  prof  jrty  of  decomposing  the  alkaline  salts,  and  forming 
with  them  acid  urates,  while  it  allows  a  portion  of  the  neutral 
salt  to  combine  with  the  excess  of  acid  expelled  in  order  to  form 


NITROGENOUS  ACIDS.         »  71 

the  urate.  In  this  manner,  acid  salts  must  be  formed  on  both 
sides. 

Uric  acid,  in  the  form  of  urate  of  soda,  is  deposited  in  the 
joints  in  great  quantity  during  gout,  though  it  is  denied  by  seve- 
ral chemists,  Garrod  and  Lehmann  among  them,  that  any  in- 
crease of  the  secretion  of  this  substance  takes  place  in  that 
disease. 

This  acid  also  exists  in  the  blood,  both  in  health  and  in 
disease. 

Uric  acid  is  undoubtedly  an  excrementitious  substance,  and  is 
in  all  probability  one  of  the  intermediate  stages  between  decom- 
posed tissue  and  urea,  the  latter  substance  resulting  from  its 
oxidation.  The  experiments  of  Wohler  and  Frerichs  on  uric 
acid  show  that  when  it  is  injected  into  the  veins  or  introdr.ced 
into  the  stomach,  the  urea  and  the  oxalate  of  lime  in  the  urine 
are  increased,  a  fact  which  is  regarded  as  conclusive  proof  of  the 
theory  just  mentioned.  Anything,  therefore,  diminishing  or 
retarding  the  oxidation  of  this  acid,  must  give  rise  to  an  increase 
of  the  unchanged  substance  in  the  urine. 

INOSIC  ACID. 

Liebig  obtained  this  acid  from  the  juice  of  flesh,  after  crea- 
tine had  crystallized  out,  by  treating  it  with  alcohol  till  crystals 
formed,  redissolving  these  in  hot  water,  precipitating  by  chlo- 
ride of  barium,  and  decomposing  with  sulphuric  acid.  It  is  a 
syrupy  fluid,  soluble  in  water,  insoluble  in  alcohol  and  ether, 
reddening  litmus  strongly,  and  having  an  agreeable  taste  of  the 
juice  of  meat. 

Liebig's  formula,  calculated  from  the  baryta  salt,  is  CjgHgNg 
Ojo+HO.  Its  atomic  weight  is  2175,  its  saturating  capacity, 
4.597. 

GLYCOCHOLIC  ACID. 

This  acid  is  obtained  by  precipitating  fresh  bile  with  sugar  of 
lead,  extracting  the  precipitate  with  boiling  alcohol  of  85  per 
cent.,  passing  sulphuretted  hydrogen  through  the  solution,  fil- 


72 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


Fig.  13. 


tering,  adding  water,  and  allowing  the  mixture  to  stand  till  the 
acid  is  deposited  in  crystals. 

It  forms  very  delicate  needles,  of  a  bitterish  sweet;  taste,  solu- 
ble in  120.5  parts  of  hot  and  303  of  cold  water,  easily  soluble 

in  alcohol,  but  slightly  in  ether. 
It  dissolves  readily  in  alkalies, 
and  is  precipitated  from  them, 
as  a  resinous  mass,  by  the  addi- 
tion of  acids.  Prolonged  boiling 
with  caustic  potash  or  baryta  wa- 
ter resolves  it  into  cholic  acid  and 
glycine. 

Its  formula  is  C^^H.^NOji  +  HO. 
The  atomic  weight  of  the  hypothe- 
tical anhydrous  acid  is  5700,  its 
saturating  capacity,  1.754. 

This  acid  is  found  in  the  bile  of 
all  animals  yet  examined  for  it  with 
the  exception  of  the  pig.  It  is 
manifestly  cholic  acid  conjugated  with  glycine,  but  of  its  origin 
or  use  nothing  is  yet  positively  known. 


Glycocholic  acid. 


TAUROCHOLIC  ACID. 

This  is  an  acid  conjugated  with  taurine,  as  the  one  last  de- 
scribed is  with  glycine.  It  is  obtained  from  the  bile  by  preci- 
pitating first  with  acetate  of  lead,  filtering,  and  precipitating 
the  filtrate  with  basic  acetate  of  lead,  to  which  a  little  ammonia 
may  be  added.  The  precipitate  is  decomposed  with  carbonate 
of  soda,  filtered,  and  extracted  with  alcohol.  Ether,  added  to 
the  alcoholic  solution,  precipitates  taurocholate  of  soda,  as  a 
resinous,  semifluid,  yellow  mass.  This  is  to  be  dissolved  in 
water,  the  solution  precipitated  with  acetate  of  silver,  the  fil- 
tered fluid  thrown  down  with  acetate  of  lead,  the  precipitate 
suspended  in  water  and  decomposed  with  sulphuretted  hydrogen. 
Sulphuret  of  lead  is  filtered  off",  and  the  clear  solution,  evapo- 
rated in  alcohol,  gives  tolerably  pure  taurocholic  acid. 

This  substance  was  formerly  called  hilinj  and  has  also  received 


NON-NITROGENOUS  ACIDS.  73 

the  name  of  cJioleic  acid.  It  dissolves  fat,  fatty  acids,  and  cho- 
lesterin  in  large  quantities;  boiled  with  alkalies,  it  is  decom- 
posed into  taurin  and  cholic  acid. 

Its  formula  is  Cj^H^sNSgO,^. 

It  is  found  in  the  bile  of  most  animals,  and  probably  exists 
in  that  of  man.  Its  origin  and  chemical  action  upon  the  food 
are  alike  unknown. 


CHAPTER    VII. 

XON-NITROGENOUS  ACIDS. 

The  acids  of  the  human  body  which  do  not  contain  nitrogen 
are  very  numerous.  For  the  sake  of  perspicuity,  they  have 
been  divided  into  several  groups. 

THE  BUTYRIC  ACID  GROUP. 

The  general  formula  of  this  group  is  CnHn_j03  4-II0. 

The  acids  composing  it  form  salts  which  are  usually  soluble, 
and  easy  of  crystallization.  They  were  formerly  called  volatile 
fatty  acids,  but  that  name  is  now  abandoned  by  most  chemists, 
because  it  was  based  upon  a  misconception  of  their  true  origin. 

From  these  acids,  may  be  obtained  a  series  of  liquid  volatile 
fluids,  called  aldehydes,  which,  on  exposure  to  the  air,  absorb 
oxygen,  and  are  converted  into  their  corresponding  acids.  Their 
general  formula  is  CnlIn_iO-fHO. 

Isomeric  with  them  is  another  series  of  compounds  obtained 
from  the  dry  distillation  of  the  baryta  salts  of  these  acids.  They 
are  oily,  volatile,  pungent  fluids,  soluble  in  alcohol  and  ether, 
but  not  in  water,  volatilizing  without  decomposition,  and  devoid 
both  of  acid  and  basic  properties.  They  are  distinguished  by 
the  termination  in  al.  Their  isomerism  wdth  the  aldehydes  may 
be  seen  by  the  following  example.  Butyric  aldehyde,  CglljO-f- 
H0=(CH)302,  hutyral 


74  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

There  is  still  another  series  of  derivatives,  known  by  the  ter- 
mination one,  obtained  from  the  strong  basic  salts  of  these  acids 
by  heating  them.  The  acid  loses  the  elements  of  carbonic  acid, 
■which  remains  combined  with  the  base,  and  a  colorless,  volatile, 
pungent,  highly  inflammable  oil  distils  over.  Thus,  hutyrate  of 
lime,  when  heated,  is  resolved  into  carbonate  of  lime  and  huty- 
rone,  e.g.  CaO,C3H,03=CaO,C02+C,H,0. 

These  acids  are  excellent  exemplifications  of  the  substitution 
theory,  the  hydrogen  in  them  being  replaceable  by  other  ele- 
ments, especially  chlorine,  iodine,  and  bromine.  Thus,  when 
chlorine  and  acetic  acid  come  together,  hydrochloric  and  chlor- 
acetic  acids  are  formed,  for  C,H303.IIO  +  6Cl=3IICl  +  C4Cl3 
O3.HO. 

Amides  are  also  formed  from  the  ammonia  salts  by  the  loss 
of  an  atom  of  water.  Acetate  of  ammonia  is  resolved  into 
acetamide  and  water;  H3N.C,H303=H,N.CJl302+nO.  The 
substitution  theory  is  inapplicable  to  these  changes.  The  amides 
are  solid,  crystallizable,  colorless,  indifferent,  volatile  substances. 
Treated  with  nitrous  acid,  they  are  converted  into  the  acids 
with  the  development  of  ammonia. 

When  the  amides  of  these  acids  are  treated  with  anhydrous 
phosphoric  acid,  they  lose  water,  and  nitriles  remain,  which 
contain  the  radicle  of  the  acid  and  one  equivalent  of  nitrogen 
in  place  of  three  of  oxygen.  Thus  hutyrmnide  and  phosphoric 
acid  form  hydrated  phosphoric  acid  and  butyronitrile ;  CgHgNOg 
+  PO,=  PO,2HO-l-C3H,N. 

The  7iitriles  are  oily,  volatile,  odorous  fluids,  less  soluble  in 
water  than  in  alcohol  or  ether ;  can  be  distilled  without  decom- 
position, and  are  neither  acid  nor  basic.  Kolbe  regards  these 
acids  as  carbo-hydrogens  conjugated  with  oxalic  acid. 

OXALIC  ACID. 

This  acid  is  a  product  of  the  oxidation  of  most  animal  and 
vegetable  substances,  and  is  usually  obtained  by  decomposing 
sugar  or  starch  with  slightly  dilute  nitric  acid,  and  crystallizing. 

It  crystallizes  with  three  atoms  of  water  in  oblique  rhombic 
prisms.     It  has  a  sharp  acid  taste,  but  no  odor.     It  efiloresces 


NON-NITROGENOUS  ACIDS.  75 

on  exposure  to  the  air,  losing  two  atoms  of  water,  and  when 
carefully  heated,  may  be  sublimed  without  decomposition,  but 
at  from  300°  to  340°  it  is  decomposed  into  formic  and  carbonic 
acids,  carbonic  oxide  and  water.  Boiled  with  salts  of  gold,  car- 
bonic acid  escapes,  and  finely  divided  metallic  gold  falls. 

Its  formula  is  C2O3  +  HO;  its  atomic  weight  450;  its  saturating 
capacity,  22.222.  It  has  been  variously  regarded  as  the  oxide 
of  a  hypothetical  radical  oxalyl,  CgOg,  a  dinoxide  of  carbonic 
oxide,  or  a  hydrogen  acid  CgOjH. 

Oxalate  of  lime  is  an  important  salt  in  pathological  chemistry, 
being  a  very  frequent  urinary  deposit.  It  is  amorphous  to  the 
naked  eye,  but  under  the  microscope  is  seen  to  be  crystallized 
in  square  octahedra,  resembling  chloride  of  sodium,  from  which 
they  are  distinguished  by  their  insolubility  in.  water. 

Oxalic  acid  is  recognized  by  its  behavior  with  salts  of  gold, 
which  it  reduces  to  the  metallic  state,  and  by  its  not  charring 
when  heated,  or  mixed  with  sulphuric  acid. 

Oxalic  acid  was  long  regarded  as  a  purely  pathological  pro- 
duct, but  it  has  been  shown  that  it  is  a  constituent  of  normal 
human  urine.  Schmidt  supposed  that  it  was  formed  from  the 
mucus  of  the  bladder,  but  Lehmann  has  obtained  it  from  urine 
thoroughly  deprived  of  its  mucus.  It  is  increased  in  a  great 
variety  of  diseases,  especially  those  accompanied  by  pulmonary 
obstruction,  or  by  weakness  of  the  respiratory  act.  It  is  also 
augmented  by  the  use  of  sparkling  wines  and  of  beer  highly 
charged  with  carbonic  acid,  as  Avell  as  of  vegetable  food  con- 
taining oxalates. 

Thus,  it  may  be  transmitted  directly  from  the  food  to  the 
urine,  but  its  usual  mode  of  production  is,  most  probably,  an  in- 
complete oxidation  of  uric  acid  and  other  constituents  of  the 
blood,  that  process  being  arrested  before  the  formation  of  car- 
bonic acid  could  be  accomplished.  It  is  easy  to  explain,  on  this 
view,  the  increase  of  this  substance  after  the  ingestion  of  car- 
bonic acid,  and  during  the  various  disturbances,  functional  or 
structural,  of  the  respiratory  organs. 


76  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


FORMIC  ACID. 

This  acid  does  not  exist,  so  far  as  yet  known,  in  the  human 
body.  It  was  originally  obtained,  as  its  name  implies,  from 
ants,  by  distillation.  Even  in  them,  however,  it  appears  to  have 
existed  in  the  food,  and  not  to  be  formed  in  the  body.  It  is  a 
common  result  of  the  oxidation  of  various  animal  and  vegetable 
substances.  It  is  usually  obtained  by  distilling  a  mixture  of  a 
little  dilute  sulphuric  acid  with  three  parts  of  sugar,  and  one  of 
bichromate  of  potash. 

It  forms  two  distinct  hydrates,  reduces  the  oxides  of  silver 
and  mercury,  and  is  decomposed  into  water  and  carbonic  oxide 
by  the  action  of  sulphuric  acid. 

Its  composition  is  C2HO3HO  ;  its  atomic  weight  462.5  ;  its 
saturating  capacity,  21.62.  It  has  been  regarded  as  an  oxalic 
acid  conjugated  with  hydrogen,  and  as  an  oxide  of  an  hypothe- 
tical radical  formyly  C2H,  which  is  believed  to  occur  in  other 
combinations,  as  for  instance  in  cldoroform  (terchloride  of 
formyl),  C2H,Cl3. 

ACETIC  ACID. 

This  is  a  well  known  result  of  the  oxidation  of  alcohol.  To 
it  our  common  vinegar  owes  its  acidity.  A  variety  of  methods 
have  been  used  to  obtain  it.  It  is  most  conveniently  procured, 
for  ordinary  chemical  purposes,  by  distilling  a  mixture  of  dilute 
sulphuric  acid,  sulphate  of  soda,  and  neutral  acetate  of  lead. 

In  its  most  concentrated  state  it  is  a  crystalline  mass  below 
60°  ;  above  this  temperature  it  is  fluid,  has  a  specific  gravity  of 
1.080,  and  boils  at  243.1°. 

Its  formula  is  C4H3O3,  HO  ;  its  atomic  weight  (anhydrous), 
637.5  ;  its  saturating  capacity,  15.686. 

Nitrate  of  suboxide  of  mercury  precipitates  from  it,  after 
some  time,  minute  crystalline  specks,  falling  in  glistening,  fatty- 
looking  scales.  It  strikes  a  red  tint  with  persalts  of  iron,  a 
property  which  it  possesses  in  common  with  meconic  and  hydro- 
sulphocyanic  acids.     From  the  former  it  is  distinguished  by  its 


NON-NITROGENOUS  ACIDS.  7T 

property  of  dissolving  lime  ;  from  the  latter  bj  the  fact  that, 
sulphocyanide  of  iron  is  precipitated  blue  hj  ferridcyanide  of 
potassium^  after  being  warmed  awhile  with  it. 

It  is  uncertain  whether  this  acid  is  found  ready  formed  in  the 
healthy  human  body.  It  is  one  of  the  products  of  the  digestion 
of  alcohol,  and  is  often  found  in  the  gastric  juice  of  dyspeptics. 
It  has  been  discovered  in  vomited  matters,  when  only  vege- 
tables and  meat,  and  no  vinegar,  had  been  eaten. 

METACETONIC  ACID. 

This  acid,  which  is  closely  allied  in  some  respects  to  nitric 
acid,  has  been  supposed,  from  analogy,  to  exist  in  the  human 
body,  though  it  has  never  been  detected  in  it.  It  is  formed 
during  the  spontaneous  decomposition  of  many  vegetable  sub- 
stances, in  the  oxidation  of  albuminous  bodies,  and  the  fer- 
mentation of  glycerin  with  yeast.  It  is  ordinarily  prepared  by 
treating  one  part  of  sugar  with  three  of  hydrated  potash,  and 
separating  the  other  acids,  oxalic,  formic,  and  acetic  from  it. 

It  has  also  been  called  hutyro-acetic  and  2y'^opionic  acid.  It 
forms,  when  concentrated,  a  colorless,  oily  fluid,  solidifying  at  a 
low  temperature,  boiling  at  about  285°,  and  having  a  peculiar 
taste,  resembling  that  of  sauer-kraut. 

Its  composition  is  CgH303.HO  ;  its  atomic  weight  (anhydrous) 
815.5  ;  its  saturating  capacity,  12.31.  Kolbe  regards  it  as  an 
ethyloxalic  acid. 

BUTYRIC  ACID. 

This  acid  is  present  in  rancid  butter,  and  was  obtained  by 
Chevreul  during  the  saponification  of  butter.  It  is  usually  pre- 
pared by  mixing  sugar,  sour  milk,  and  cheese  together,  and  ex- 
posing them  for  five  or  six  weeks,  or  as  long  as  gas  escapes,  to 
a  summer  temperature,  i.  e.  from  85°  to  95°.  The  fluid  is 
filtered,  decomposed  with  carbonate  of  soda,  filtered  again,  con- 
centrated, decomposed  with  sulphuric  acid,  and  distilled.  The 
butyric  acid,  which  comes  over,  is  freed  from  water  and  acetic 
acid  by  fused  chloride  of  calcium. 

It  is  an  oily  fluid,  and  can  only  be  solidified  by  the   intense 


78  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

cold  ( — 183°)  induced  by  mixing  solid  carbonic  acid  with  ether, 
when  it  crystallizes  in  plates.  It  evaporates  at  the  ordinary 
temperature,  but  does  not  boil  below  315°.  When  inflamed,  it 
burns  like  an  ethereal  oil. 

Its  formula  is  C8H^03.HO  ;  its  atomic  weight  (anhydrous), 
987.5;  its  saturating  capacity,  10.120. 

It  has  been  found  in  the  milk,  the  feces,  the  urine  of  preg- 
nant women,  and  women  who  do  not  suckle  their  children,'  the 
sweat,  especially  of  the  genitals  and  the  lower  extremities.  The 
nauseous,  acrid,  or  rancid  substances  occasionally  vomited  from 
the  stomach,  undoubtedly  owe  this  odor  to  butyric  acid.  When 
met  with  in  the  primse  vise,  it  is  probably  formed  from  the  non- 
nitrogenous  constituents  of  the  food.  When  it  occurs  in  the 
sweat,  blood,  and  urine,  it  is  most  likely  a  result  of  regressive 
metamorphosis,  owing  its  origin  to  the  disintegration  of  the  tis- 
sues, or  the  gradual  oxidation  of  the  fats. 

VALERIANIC   ACID. 

This  acid,  as  well  as  others  of  this  group  whose  amount  of 
carbon  is  divisible  by  two  and  not  by  four,  has  never  been  found 
in  the  human  body.  It  is,  however,  interesting,  as  one  of  the 
results  of  decomposition  of  animal  and  vegetable  matter. 

It  has  a  characteristic  odor,  an  acrid,  burning  taste,  and  pro- 
duces a  white  spot  on  the  tongue.  It  remains  fluid  at  5°,  boils 
at  349°,  and  dissolves  in  26  parts  of  water. 

Its  formula  is  CjoHp03.HO  ;  its  atomic  weight  (anhydrous), 
1162.5  ;  and  its  saturating  capacity,  8.602. 

CAPROIC  ACID. 

This  is  a  somewhat  thin  liquid  with  an  odor  resembling  that 
of  sweat.  It  is  obtained  by  saponifying  butter,  or  decomposing 
oleic  acid  with  fuming  nitric  acid,  or  by  acting  on  albuminous 
bodies  with  peroxide  of  manganese  or  chromic  acid. 

Its  formula  is  CjjHjjOj.HO  ;  its  atomic  weight  (anhydrous), 
1337.5;  its  saturating  capacity,  7.476.  Kolbe  regards  it  as 
amyloxalic  acid. 


NON-NITROGENOUS  ACIDS.  79 

From  its  odor,  it  has  been  supposed  to  exist  in  sweat.  Leli- 
mann  says,  it  has  not  been  sought  for  in  the  contents  of  the 
stomach  or  in  the  urine.  It  happened  to  the  author,  on  one 
occasion,  while  making  the  analysis  of  the  contents  of  a  negro's 
stomach  for  arsenic,  to  use  Reinsch's  test  in  a  portion  of  the 
fluid  not  thoroughly  freed  from  organic  matter.  The  brilliant 
surface  of  the  copper  became,  after  protracted  boiling,  covered 
■with  an  olive-brown,  slightly  lustrous  coating,  which  dissolved 
in  caustic  ammonia ;  and,  when  heated,  burned  with  a  green  flame, 
emitting  the  characteristic  odor  of  negro's  sweat.  No  farther 
examination  of  it  was  made,  and  the  fact  is  here  stated  for  what 
it  is  worth. 

(ENANTHYLIC  ACID. 

This  is  a  colorless,  oily,  inflammable  liquid,  of  a  faint  aroma- 
tic odor  and  taste,  produced  during  the  decomposition  of  fats. 
It  is  usually  obtained  by  the  action  of  nitric  acid  on  castor- oil. 
Its  formula  is  C14H13O3.HO. 

CAPRYLIC  ACID. 

This  is  another  of  the  acids  formed  during  the  saponification 
of  butter,  and  by  the  reaction  of  nitric  and  oleic  acids.  Its 
formula  is  Ci6Hj^03.HO. 

Pelargonic  acid  {G^^^^O^.^0^  found  in  several  plants  and 
produced  by  acting  on  oleic  or  choloidic  acid,  by  nitric  acid; 
capric  acid  (C2oHjg03.HO),  obtained  from  oil  of  rue,  and  cetylio 
acid  (€32113^03. HO),  procured  from  spermaceti,  require  no  spe- 
cial notice  here. 


SUCCINIC  ACID  GROUP. 

The  general  formula  of  these  acids  is  CnHn_203.H0.  They 
are  products  of  the  decomposition  of  animal  matters,  especially 
of  the  fats.  They  are  all  formed  by  the  action  of  nitric  on 
oleic  acid.     They  are  crystallizable,  volatile  at  a  high  heat  with 


80 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


a  suffocating  odor,  and  yield  oxalic  acid  when  fused  with  hydrate 
of  potash.  None  of  them  are  preformed  in  the  animal  body, 
and  their  only  physiological  interest  consists  in  their  being  pro- 
ducts of  decomposition. 

Succinic  acid{G^\OyllO),  as  its  name  implies,  was  originally 
obtained  by  the  dry  distillation  of  amber.     It  occurs,  however, 

as  a  product  of  the  decomposition  of 
fat  and  of  various  kinds  of  ferment- 
ation. When  perfectly  anhydrous, 
it  occurs  in  very  delicate  needles, 
with  one  atom  of  water ;  it  crystal- 
lizes in  oblique  rectangular  prisms. 

Sehacic  acid  (CjoHgOg.HO)  is  ob- 
tained during  the  dry  distillation  of 
oleic  acid.     It  forms  white,  nacreous, 
acicular    crystals    grouped   in   loose 
heaps.     It  fuses  at  260°  into  a  color- 
less liquid,  which,  on  cooling,  solidi- 
fies into   a    crystalline  mass.     It  is 
slightly  soluble  in  cold  water,  freely 
in  hot  water,  alcohol,  and  ether.     It  reddens  litmus,  has  a  pun- 
gent taste,  and  is  converted,  by  nitric  acid,  into  paratartaric 
acid.     Its  formula  is  CjoHgOj.HO. 


Sebacic  acid. 


BENZOIC  ACID  GROUP. 

The  general  formula  of  this  group  is  Cnlln— 9O3.HO.  With 
the  exception  of  benzoic  acid,  they  possess  but  little  interest  for 
the  physiologist.  They  are  solid,  crystallize  readily  in  needles 
or  scales,  are  fusible,  slightly  soluble  in  cold,  readily  in  hot 
water.  They  have  aldehydes,  amides,  and  nitriles  like  the  acids 
of  the  former  group. 

Benzoic  acid  (CJ4H5O3.HO)  is  the  only  one  to  which  we  shall 
call  attention.  It  is  a  pharmaceutical  substance,  and  is  com- 
monly obtained  by  the  sublimation  of  gum  benzoin.  When  thus 
procured,  it  occurs  in  colorless,  delicate  needles;  obtained  in  the 
moist  way,  it  crystallizes  in  scales,  minute  prisms,  or  six-sided 


NON-NITROGENOUS  ACIDS. 


81 


needles.     It  fuses  at  about  250°,  boils  Fig.  15. 

at  462°,  being  converted  into  a  thick, 
irritating  vapor,  and  it  is  not  decom- 
posed by  sulphuric  or  nitric  acid.  The 
products  of  its  metamorphosis  are  oil  of 
bitter  almonds,  benzamide,  and  several 
other  substances,  "which  have  recently 
been  very  carefully  studied,  but  which 
we  have  not  room  here  to  consider. 

The  influence  of  benzoic  acid,  in 
increasing  the  quantity  of  hippuric 
acid  in  the  urine  has  already  been  no- 
ticed.    Liebig   thought,   at  one  time, 

that  it  was  discharged  originally  in  the  urine  of  ill-fed  and  hard- 
worked  horses ;  changing  his  former  view,  that  it  was  a  product 
of  decomposition  out  of  the  body.  The  subject  has  been  ex- 
amined by  Lehmann,  and  he  has  come  to  the  conclusion  that 
Liebig's  earlier  opinion  is  the  correct  explanation  of  its  forma- 
tion. 


Benzoic  acid. 


LACTIC  ACID  GROUP. 

The  formula  of  this  group,  which  contains  but  few  individual 
acids,  is  CnHn_j05.H0;  when  deprived  as  much  as  possible  of 
water,  they  are  oily,  non-crystallizable  fluids. 

Lactic  acid  (CgHjOj.HO),  in  its  most  concentrated  state,  is  a 
colorless,  inodorous,  thick,  syrupy  fluid,  of  specific  gravity  1.215; 
soluble  in  water,  alcohol,  and  ether,  attracting  water  from  the 
air,  decomposing  by  heat,  and  displacing  many  oxides  from 
their  salts.  The  relations  of  the  acid  differ,  as  it  is  obtained 
from  muscular  juice;  or  from  sugar,  especially  in  the  amount 
of  water  of  crystallization  and  the  degree  of  solubility  of  the 
salts. 

It  is  formed  during  the  fermentation  of  fluids  containing  sugar 
or  starch.  Bensch's  process  is,  to  mix  6  parts  of  cane-sugar,  y'g 
of  tartaric  acid,  8  of  sour  milk,  i  of  old  cheese,  3  of  levigated 
chalk,  and  26  of  water,  and  to  expose  them  for  eight  or  ten 
days  to  a  temperature  of  90°.  A  semi-solid  magma  of  lactate 
6 


82  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

of  lime  is  formed,  which  is  boiled  with  20  parts  of  water  and 
Jg  of  caustic  lime,  filtered  while  boiling,  slightly  evaporated,  and 
set  aside  a  few  days  to  crystallize.  The  salt  is  dried,  pressed, 
treated  with  /^  of  sulphuric  acid,  filtered,  and  the  clear  fluid 
saturated  with  j^  of  carbonate  of  zinc  and  crystallized.  The 
zinc  and  salt  is  decomposed  with  sulphuretted  hydrogen,  and  the 
fluid  concentrated  first  by  heat,  afterwards  in  vacuo,  and  the 
hydrated  acid  obtained  by  solution  in  ether. 

Liebig  procures  it  from  the  juice  of  flesh  after  the  separation 
of  creatine. 

It  is  one  of  the  most  difficult  to  recognize  of  all  the  acids 
found  in  the  animal  body.  It  requires  a  thorough  knowledge  of 
its  various  reactions,  and  especially  of  the  microscopic  charac- 
ters of  its  salts,  to  arrive  at  anything  like  a  correct  opinion. 

The  question  so  long  discussed,  whether  free  lactic  acid  forms 
a  part  of  healthy  gastric  juice  may  now  be  considered  as  decided 
in  the  affirmative.  This  acid  is  a  constant  constituent  of  the 
juice  of  flesh,  or  the  muscular  fluid.  It  is  also  found  in  the  secre- 
tion bathing  mucous  surfaces  and  in  the  sweat.  In  diabetes 
mellitus,  it  occurs  in  the  saliva,  and  has  been  found  in  the 
blood  in  several  forms  of  disease.  It  has  not  yet  been  detected 
in  healthy  blood,  though  it  probably  exists  there,  the  failure  to 
determine  its  presence  being  due  to  the  imperfection  of  the  pre- 
sent appliances  of  analytical  chemistry,  as  well  as  to  the  rapidity 
with  which  it  is  converted  into  carbonic  acid.  Lehmann  found 
carbonate  of  soda  making  its  appearance  in  the  urine  within 
five  minutes  after  the  injection  of  lactate  of  soda  into  the  jugu- 
lar vein  of  a  dog.  It  is  also  present  in  the  urine,  in  persons 
who  have  fed  largely  on  food  containing  lactates,  or  whose 
respiratory  functions  have  been  impaired.  It  is  always  found 
in  urine  containing  any  considerable  quantity  of  oxalate  of  lime. 
It  has  been  observed  in  the  fluid  yielded  by  the  long  bones  in  a 
case  of  osteomalacia. 

The  lactic  acid,  formed  in  the  intestinal  canal,  probably 
results  from  the  decomposition  of  the  vegetable  food,  while  that 
in  the  muscles  would  appear  to  arise  from  the  metamorphosis  of 
various  animal  substances,  among  others,  the  glycerine  basis  of 
the  fats. 


NON-NITROGENOUS  ACIDS.      ,  83 

In  the  stomach,  it  is  supposed  to  play  an  important  part  in 
the  digestion  of  the  food ;  while  in  the  hlood,  it  seems  to  form  a 
part  of  the  respiratory  food.  In  the  7nuscles,  Liebig  supposes 
that,  by  reacting  on  the  alkaline  blood  of  the  capillaries,  it  keeps 
up  an  electric  tension  which  influences  the  function  of  the  mus- 
cles.    In  the  siveat  and  urine,  it  is  a  product  of  excretion. 

SOLID  FATTY  ACIDS. 

Lehmann  gives  as  the  general  formula  for  this  group  CmHm— ^ 
O3.HO,  which  shows  at  a  glance  the  close  relation  between  this 
and  the  first-described  group  of  non-nitrogenous  acids.  They 
differ,  however,  in  having  a  higher  atomic  weight,  and  in  several 
other  particulars.  At  common  temperatures,  they  are  solid, 
white,  crystalline,  tasteless,  inodorous,  soluble  in  ether  and  in 
boiling  alcohol,  insoluble  in  water,  inflammable,  and  fusible  be- 
low 212°.  They  leave  on  paper  a  fatty  spot  which  does  not 
disappear,  expel  carbonic  acid  from  its  salts  by  the  aid  of  heat, 
and  have  a  strong  tendency  to  form  insoluble  salts  with  metallic 
bases. 

Very  few  of  them  have  been  found  in  the  animal  body. 

MARGARIC  ACID. 

This  acid  crystallizes  in  pearly  needles  (whence  its  name), 
which  under  the  microscope  appear  interlaced  like  tufts  of  grass, 
and  arranged  in  plates  or  grouped  in  star-like  forms.  It  can 
only  be  partially  distilled  unchanged,  carbonic  acid  and  marga- 
rone  being  formed.  By  prolonged  contact  with  nitric  acid,  it 
is  decomposed  into  succinic,  suberic,  and  carbonic  acids  and 
water. 

Its  formula  is  03^113303.110,  its  atomic  weight  3262.5. 

It  is  obtained  by  saponifying  human  fat  or  olive  oil  with 
potash,  and  decomposing  with  sulphuric  acid.  The  fatty  preci- 
pitate is  well  washed  with  water,  thoroughly  dried,  and  pressed 
strongly  between  bibulous  paper  to  get  rid,  as  much  as  possible, 
of  oleic  acid.  By  repeated  crystallizations  from  hot  alcohol,  the 
stearic  acid,  which  falls  first,  is  separated ;  and  the  oleic  acid  is 
got  rid  of  by  precipitating  with  acetate  of  lead,  and  dissolving 


84  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

out  the  oleate  of  lead  with  boiling  ether.  The  margarate  of 
lead  is  decomposed  by  an  alkaline  carbonate,  and  the  resulting 
alkaline  margarate  by  a  stronger  acid. 

Margaric  acid  is  a  common  constituent  of  fats.  It  is  found 
free  in  the  feces  after  vegetable  food  or  purgative  medicine  has 
been  taken,  and  in  acid  pus  from  cold  abscesses.  The  finest 
possible  crystals  may  be  obtained  by  carefully  fermenting  pus. 

STEARIC  ACID. 

This  acid,  which  is  usually  prepared  from  mutton  fat  as 
already  described,  crystallizes  in  white  glistening  needles  or 
leaflets,  appearing  under  the  microscope  as  elongated  lozenge- 
shaped  plates,  with  the  obtuse  angles  rounded  off.  Digestion  with 
nitric  or  chromic  acid  converts  it  into  margaric  acid. 

Its  formula  is  C6gHgQ05.2HO,  its  atomic  weight,  6425. 

It  occurs  in  most  animal  fats,  and  must  be  formed  in  the  body, 
since  it  is  not  found  in  vegetable  fats.  It  is  probably  formed 
from  margaric  acid,  since  it  is  equivalent  to  two  atoms  of  that 
acid  less  one  of  oxygen. 

OILY  FATTY  ACIDS. 

This  group  contains  but  few  acids;  its  general  formula  is 

CmHni_~0,.HO. 


'm-^-^m — 3^3* 


OLEIC  ACID. 

Oleic  or  elaic  acid  is  at  ordinary  temperatures  an  oily,  limpid, 
colorless,  tasteless,  inodorous  fluid,  solidifying  at  39°  to  a  white 
crystalline  mass,  which  contracts  and  forces  out  the  still  oily 
portion.  An  alcoholic  solution,  exposed  to  intense  cold,  crys- 
tallizes in  long  needles.  It  is  decomposed  by  heat,  giving  off 
carbonic  acid  and  carbo-hydrogens,  and  forming  also  capric, 
caprylic,  and  sebacic  acids,  and  carbon. 

Its  formula  is  CjgHgjOg.HO,  its  atomic  weight  (anhydrous) 
3412.5. 

Elaidic  acid  is  isomeric  with  it,  but  crystallizes  from  alcohol 
in  large  plates  instead  of  needles. 


NON-NITROGENOUS  ACIDS.  85 

After  having  separated  the  oleate  of  lead  as  already  described, 
this  salt  is  decomposed  with  carbonate  of  soda  and  the  soda- 
salt  with  sulphuric  acid.  The  brown  oleic  acid  thus  obtained  is 
to  be  treated  with  excess  of  ammonia,  precipitated  with  chloride 
of  barium  and  the  baryta-salt ;  after  being  purified  by  repeated 
crystallizations  from  boiling  alcohol,  is  to  be  decomposed  with 
tartaric  acid,  and  thoroughly  washed  with  water. 

It  exists  in  greater  quantity  in  vegetable  than  animal  fats,  and 
is  supposed  to  serve  as  a  basis  for  the  formation  of  the  solid 
fatty  acids. 

Doeglic  acid,  having  only  been  found  in  the  oil  of  a  certain 
variety  of  whale  {haloena  rostrata),  need  not  occupy  our  atten- 
tion. 

RESINOUS  ACIDS. 
LITHOFELLIC  ACID. 

This  acid  has  only  been  obtained  from  hezoars,  the  intestinal 
concretions  of  certain  goats.  It  crystallizes  in  small  six-sided 
prisms,  volatilizes  in  white  vapors  with  an  aromatic  odor,  fuses 
at  400°,  and  solidifies  in  a  crystalline  form. 

Its  formula  is  C40H3QO7.HO. 

CHOLIC  ACID. 

CIioUc  acid  is  obtained  by  precipitating  the  alcoholic  solution 
of  bile  with  ether ;  digesting  the  resinous  mass  that  falls  with  a 
dilute  solution  of  potash  for  twenty-four  or  thirty-six  hours,  till 
the  potash  salt  begins  to  crystallize.  This  must  then  be  dis- 
solved in  water,  and  decomposed  with  hydrochloric  acid.  A  few 
drops  of  ether  convert  the  resinous  mass  into  a  crystalline,  solid, 
pulverizable  substance.  It  is  to  be  reduced  to  powder,  washed 
with  water,  crystallized  in  alcohol,  and  treated  with  ether  to 
remove  coloring  matters. 

It  crystallizes  in  tetrahedra,  octahedra,  or  rhombic  prisms ;  has 
a  bitter  taste  and  a  sweetish  after-taste ;  is  slightly  soluble  in 
water,  easily  in  alcohol,  and  with  more  difficulty  in  ether;  burns 
with  a  clear  flame,  and  is  decomposed  by  hydrochloric  acid  into 
choloidic  acid  and  dyslysin. 


86 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


Cholic  acid. 


Its  formula  is  C^gHjgOg.HO,  according  to  Strecker ;  C^Ji^fi^ 
+  5H0,  according  to  Mulder. 
It,  together  with  bile  and  biliary  derivations  which  always 

contain  it,  is  recognized  by 
Pettenkofer's  test.  The  al- 
coholic extract  is  dissolved 
in  a  little  water,  a  drop  of 
syrup  containing  one  part 
of  sugar  to  four  of  water 
let  fall  into  it,  and  pure 
English  sulphuric  acid,  free 
from  sulphurous  acid,  drop- 
ped cautiously  into  the  mix- 
ture. It  first  becomes  tur- 
bid, then,  as  the  acid  is  ' 
gradually  added,  clears  up 
again,  and  becomes  first 
yellowish,  then  cherry-red, 
then  a  deep  carmine,  then  purple,  and  finally  violet.  To  use 
this  test  properly,  excess  of  sugar  must  be  avoided,  and  the 
temperature  should  approach  but  never  exceed  122°.  The  fluid 
must  also  be  allowed  to  stand  awhile.  This  test,  however,  can-  , 
not  be  inverted,  and  used  for  the  detection  of  sugar,  for  the 
same  change  takes  place  with  acetic  acid. 

Cholic  acid  is  easily  detected  by  the  above  test  in  the  whole 
small  intestine,  and  a  diagnosis  of  the  seat  of  artificial  anus  has 
been  made  by  its  aid.  Pettenkofer  failed  to  detect  it  in  the 
healthy  feces,  though  he  found  it  in  the  discharge  of  diarrhoea. 
Lehmann,  however,  obtained  the  reaction  by  dissolving  the  alco- 
holic extract  of  feces  in  ether,  separating  the  fats  with  water, 
and  testing  the  concentrated  aqueous  solution  of  the  ethereal 
extract. 

This  substance  has  so  many  points  of  resemblance  with  the 
fatty  acids  that  it  is  thought  probable  that  it,  with  other  biliary 
substances,  is  formed  from  the  fats.  It  has  been  supposed  to  be 
oleic  acid  conjugated  with  a  radical,  C^JI^O^. 


NON-NITROGENOUS  BASES  AND  SALTS — HALOIDS. 


CHAPTEK    VIII. 

NON-NITROGENOUS  BASES  AND  SALTS— HALOIDS. 

This  is  the  title  given  by  Berzelius  to  a  class  of  organic  com- 
pounds Tvliich  differ  from  those  we  have  already  been  consider- 
ing. The  term  is  derived  from  the  Greek  word  for  salt,  and 
implies  that  these  bodies  are  analogous  to  common  salt  in  chemi- 
cal constitution.  A  word  or  two  in  reference  to  certain  peculiar- 
ities of  combination  in  the  inorganic  world  will  constitute  a  suit- 
able preface  to  our  account  of  these  organic  salts  and  their  bases. 

A  salt  is  usually  called  a  compound  of  a  base  and  an  acid, 
and  it  was  at  one  time  thought  that  all  of  them  were  made  up 
by  the  union  of  oxygen  and  a  metal  to  form  a  base,  the  union  of 
oxygen  with  a  metalloid  to  constitute  an  acid,  and  the  combina- 
tion of  these  two  bodies,  the  base  and  the  acid,  to  produce  the 
salt.  On  a  more  minute  examination,  however,  it  was  found  that 
this  was  by  no  means  the  invariable  constitution  of  salts.  It  is 
true,  undoubtedly,  of  a  very  large  number  of  this  class  of  com- 
pounds, of  which  the  sulphate  of  potash  may  be  cited  as  an 
example.  In  it,  the  component  parts  are  the  base,  potash,  the 
oxide  of  a  metal,  potassium,  and  the  acid,  sulphuric,  the  oxide 
of  a  metalloid,  sulphur.  The  formula,  therefore,  of  the  per- 
fectly anhydrous  salt  would  be  KOjSOj. 

According  to  this  view,  therefore,  common  salt  was  called  a 
muriate  of  soda,  and  the  soda  was  thought  to  be  combined  with 
the  muriatic  acid,  just  as  the  potash  is  with  the  sulphuric  acid 
in  the  last-mentioned  case.  It  was  discovered,  however,  that 
the  old  muriatic  acid  is  a  hydracid,  that  is  to  say,  that  it  contains 
no  oxygen,  but  is  formed  by  the  union  of  chlorine  and  hydro- 
gen, and  that  in  combining  with  soda,  it  loses  its  hydrogen,  and 
the  base  parts  with  its  oxygen,  so  that  there  is  a  direct  union  of 
the  metalloid  with  the  metal,  the  former  parting  with  its  acidi- 
fying, the  latter  with  its  basic  principle.  This  salt,  therefore, 
is  constituted  according  to  the  formula  Na,Cl,  a  totally  dif- 


88  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

ferent  method  of  combination  from  what  obtains  among  the 
oxysalts. 

Farther  investigations  have  shown  that  there  may  be  sulpho- 
bases,  and  sulphacids,  and  sulpho-salts;  that  is,  that  sulphur 
may  play  the  part  of  oxygen,  forming  a  base  on  one  hand  and 
an  acid  on  the  other,  and  that  these  two  substances  may  after- 
wards unite  to  form  a  substance  crystallizable,  decomposable,  and, 
in  every  respect,  entitled  to  the  appellation,  salt.  An  example 
of  this  is  found  in  the  yellow  crystals  obtained  by  evaporating 
a  solution  of  arseniate  of  potash  through  which  sulphuretted 
hydrogen  has  been  passed.  In  them,  the  potassium  is  proved 
to  exist  as  a  sulphuret  or  a  sulpho-base,  and  the  acid  also  as  a 
sulphuret  or  sulphacid.  There  are  other  substances  which  exhi- 
bit the  same  properties  in  this  respect  as  sulphur.  From  these 
peculiarities  two  classes  of  salts  have  been  established,  the 
amphid  salts,  which,  like  sulphate  and  sulpharseniate  of  potash, 
consist  of  an  acid  and  a  base,  each  of  which  is  composed  of  two 
elements ;  and  the  haloid  salts,  in  which  there  is  direct  union 
between  a  metal  and  a  halogen  (for  so  iodine,  chlorine,  bromine, 
and  the  compound  substances,  such  as  cyanogen,  which  form 
salts  of  this  type,  have  been  called). 

Ammonia,  being  a  compound  body,  furnishes  an  excellent 
example  of  these  two  modes  of  combination.  This  substance 
when  free  as  a  gas  is  represented  by  the  formula  NII3.  In  this 
form,  it  unites  with  the  dry  oxacids  to  form  substances  called 
by  Rose  ammones,  which  are  totally  different  from  the  salts  of 
the  same  acids,  the  latter  being  never  formed  without  the  inter- 
vention of  water.  The  chlorine  salt  of  ammonia  was  formerly 
supposed  to  have  the  constitution  NH3,HC1.  The  analogy  of 
other  chlorides,  however,  compelled  chemists  to  assume  a  new 
radical  (NH^)  having  the  nature  of  a  metal;  a  view  which  is 
strengthened  by  the  formation  of  the  ammoniacal  amalgam. 
Hence,  the  chloride  is  represented  as  NH^Cl.  The  oxysalts, 
which  were  formerly  regarded  as  combinations  of  the  acids  with 
ammonia,  united  with  one  atom  of  water,  are  now  considered  to 
be  formed  by  the  union  of  the  acid  Avith  an  oxide  of  the  base 
NH^.  Thus,  sulphate  of  ammonia,  instead  of  being  NH3,S0, 
HO,  is  now  expressed  by  the  formula  NH40,S03. 


NON-NITROGENOUS  BASES  AND  SALTS — HALOIDS.  89 

Now,  if  these  metamorphoses  of  ammonia  bo  compared  with 
the  constitution  of  the  alkaloids,  and  of  the  bases  of  the  fats, 
it  will  be  found  that  the  theory  which  supposes  the  basicity  of 
the  nitrogenous  alkaloids  to  be  explicable  on  the  hypothesis  of 
a  conjugated  ammonia,  will  not  hold  good  in  the  case  of  the 
latter  class  of  bodies.  They  are  basic  also,  and  contain  no 
nitrogen.  We  have  seen,  however,  that  an  acid  may  combine 
with  the  oxide  of  a  compound  of  nitrogen  and  hydrogen,  and 
we  may  suppose  that  the  same  union  may  take  place  with  the 
oxide  of  a  hydrocarbon.  These  oxides,  however,  are  just  as  un- 
known in  their  isolated  state,  as  is  the  oxide  of  ammonia,  and 
many  of  them,  ether  for  example,  were  for  a  long  time  not  sus- 
pected of  being  basic.  They  form  both  acid  and  neutral  salts, 
the  former  of  which  have  been  classified  among  the  conjugated 
acids,  and  the  latter  not  regarded  as  salts  at  all. 

OXIDE  OF  LIPYL. 

When  any  of  the  fats  are  boiled  in  water  with  the  alkalies, 
the  alkaline  earths,  or  the  oxides  of  the  metals,  compounds  are 
formed  between  the  fatty  acids  and  the  inorganic  bases,  while  a 
sweet,  uncrystallizable  substance  remains,  which  has  been  called 
glycerine.  On  weighing  the  products,  an  increase  of  weight  is 
found  to  have  taken  place,  and  this  can  only  come  from  the 
water  which  is  essential  to  the  operation.  It  was  supposed  that 
these  facts  could  be  explained  by  assuming  that  the  fatty  acid 
was  combined  with  glycerine,  from  which  it  was  separated  by  the 
stronger  affinity  of  the  inorganic  bases.  On  examination,  how- 
ever, it  was  discovered  that  the  body  combined  with  the  fatty 
acid  was  composed  according  to  the  formula  CgHjO,  while  the 
investigation  of  glycero-sulphuric  acid  showed  that  glycerine 
must  be  expressed  by  CgH^Oj.  It  is,  therefore,  probable  that 
the  true  base  of  the  fats,  not  yet  isolated,  and  to  which  Berze- 
lius  has  given  the  name  of  Oxide  of  Lipyl  (lipyl  being  the  hypo- 
thetical radical  C3H2),  has,  during  the  process  of  decomposition, 
assimilated  water,  and  been  converted  into  a  new  body,  glycerine. 


90       '  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


GLYCETRINE. 

When  the  fluid  which  remains  after  the  manufacture  of  lead 
plaster  is  examined,  it  is  found  to  contain  an  organic  substance, 
and  a  little  oxide  of  lead.  If  the  latter  be  thrown  down  by 
passing  a  stream  of  sulphuretted  hydrogen  through  the  solution, 
a  black  sulphuret  of  lead  subsides,  and  the  watery  solution-  of 
glycerine  remains.  This  is  to  be  evaporated  first  in  the  water- 
bath,  and  then  in  vacuo. 

Thus  obtained,  it  is  a  pale-yellowish  fluid,  sweet  to  the  taste, 
attracting  water  from  the  atmosphere,  soluble  in  water  and  alco- 
hol, but  not  in  ether,  inflammable,  and  indifi"erent  towards  the 
vegetable  colors.  It  dissolves  the  alkalies  and  metallic  oxides, 
and,  when  oxidated,  gives  rise  to  a  variety  of  acids,  which 
differ  with  \the  degree  of  oxidation.  By  ordinary  fermentation 
it  is  converted  into  metacetonic  acid. 

Pelouze's  formula  for  it  is  CgH^Oj.HO.  It  is  not  a  hydrate  of 
the  oxide  of  lipyl,  but  a  distinct  body,  which  unites  with  acids 
to  form  acid  salts,  that  have  been  usually  regarded  and  named 
as  compound  acids.  The  products  of  its  metamorphosis  are 
acrolein,  acrylic  acid,  and  disacrone. 

The  best  test  for  glycerine  is  to  heat  it  rapidly  alone,  or  with 
a  little  anhydrous  phosphoric  acid,  when,  if  it  be  sufiiciently 
diluted,  the  peculiar  and  disagreeable  odor,  resembling  that  of 
the  wick  of  a  half-extinguished  oil-lamp,  is  developed. 

Glycerine  has  been  found  in  the  yolk  of  the  egg,  and  in  the 
fats  of  the  brain,  in  the  form  of  the  phosphate  of  glycerin- 
ammonia.  It  has  been  supposed  that,  during  the  oxidation  of 
the  fats  in  the  organism,  glycerine  is  formed,  and  subsequently 
converted  into  metacetonic  acid. 

SALTS  OF  OXIDE  OF  LIPYL  OR  FATS. 

These  substances  are  usually  soft  and  greasy  at  common 
temperatures,  though  some  of  them  are  firm  and  waxy,  and  a 
few  liquid.  When  pure,  they  exert  no  action  upon  vegetable 
colors,  but,  on  exposure  to  the  air,  become  rancid  and  acid. 
They  are  inodorous  when  fresh,  or  at  most,  give  ofi"  a  faint,  pe- 


NON-NITROGENOUS  BASES  AND  SALTS— HALOIDS.  91 

culiar  smell,  are  insoluble  in  water,  but  very  soluble  in  ether  ; 
and,  "when  exposed  to  a  strong  heat,  with  free  access  of  oxygen, 
they  burn  with  a  clear  flame.  Certain  ferments  resolve  them 
into  glycerine  and  fatty  acids.  Among  these  ferments  are  the 
putrid  albuminous  substances,  and  the  pancreatic  fluid. 

Stearin  (stearate  of  oxide  of  lipyV)  is  a  pure  white  substance, 
crystallizing  in  snowy,  glistening  scales,  which,  under  the  micro- 
scope, appear  as  quadrangular  tablets.  It  melts  at  144°,  solidi- 
fies without  crystallizing;  is  brittle;  when  dry,  a  non-conductor 
of  electricity,  and  yields  stearic  acid  when  saponified. 

Margarin  {^margarate  of  oxide  of  lipyl)  crystallizes  in  pearly 
needles,  grouped  in  whorls ;  melts  at  118°,  dissolves  slightly  in 
alcohol,  readily  in  hot  ether,  and  separates  from  these  solutions 
in  pearly  scales. 

Olein  [oleate  of  oxide  of  IvpyT),  or  elain,  is  a  colorless  oil ; 
solidifying  at  a  low  temperature ;  a  non-conductor  of  electricity ; 
becoming  rancid  on  exposure  to  the  air ;  never  entirely  free  from 
margarin  and  stearin,  and  when  saponified,  yielding  glycerine, 
oleic  acid,  and  more  margaric  acid  than  the  margarin  mixed 
with  it  contains. 

The  usual  method  of  obtaining  these  substances  is  to  purify 
common  fat  by  repeated  meltings  and  washings  in  water,  to 
dissolve  this  in  boiling  alcohol,  and  allow  it  to  cool,  when  mar- 
garin and  stearin  separate  in  scales,  and  the  solution  contains  the 
olein.  Pure  margarin  is  best  obtained  from  those  fats  which  do 
not  contain  stearin.  Olein  is  sometimes  obtained  by  digesting 
with  half  the  saponifying  quantity  of  potash ;  the  stearin  and 
margarin  are  saponified,  and  the  olein  remains  unchanged. 

Fats  are  widely  diff"used,  not  only  through  the  animal,  but 
also  through  the  vegetable  world.  Some  of  these  fats  have  been 
found  isolated  from  the  others,  and  crystallized. 

In  the  human  body,  fat  is  always  found  in  the  orbit  of  the  eye, 
around  the  heart,  and  among  the  muscles  of  the  face,  even  after 
the  most  wasting  diseases.  It  is  also  abundant  in  the  subcu- 
taneous cellular  tissue,  the  omentum,  the  feonale  breast,  and  about 
the  kidneys.  The  onarroiv  of  the  bones  is  only  a  liquid  fat. 
The  minimum  of  fat,  and  very  often  none  at  all,  is  to  be 
found  in  the  pulmonary  tissue,  the  glans  penis,  and  the  clitoris. 


92  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

In  the  fluids,  it  constitutes  from  0.14  to  0.33^  of  normal  blood. 
The  chyle  and  lym^h  both  contain  fat,  the  former  being  very 
rich  in  it. 

The  period  of  life  influences  very  much  the  deposition  of  fat. 
It  is  most  abundant  in  childhood,  less  so  in  youth,  and  increas- 
ing again  later  in  life.  Women  have  more  fat  than  men.  Ex- 
treme activity  of  the  sexual  functions  has  been  usually  considered 
to  diminish  the  amount  of  fat  in  the  system.  This  is  not  the 
case  in  women,  as  it  is  well  known  that  nearly  all  prostitutes, 
who  do  not  destroy  their  health  by  ardent  spirits,  late  hours, 
and  the  other  excesses  incident  to  their  unhappy  calling,  have  a 
decided  tendency  to  emhoniJoint.  Old  maids,  on  the  other  hand, 
even  long  before  the  decay  of  their  sexual  functions,  are  noted 
for  their  leanness.  Neither  does  the  rule  always,  nor,  accord- 
ing to  most  men's  experience,  generally,  hold  good  with  men. 
The  most  notorious  rakes  are  often  very  fat,  and  those  ascetics, 
who  are  known  to  be  continent,  are  not  found  to  be  fatter  than 
men  who  do  not  put  such  restraints  upon  their  appetite.  Short 
of  actual  diseased  excitement  of  these  functions,  we  do  not  be- 
lieve that  even  the  male  sex  is  emaciated  by  their  moderate  ex- 
ercise, unless,  indeed,  there  should  be  some  morbid  tendency  in 
the  system  which  any  indulgence  may  kindle  into  actual  disease. 

Great  muscular  activity,  conjoined  with  a  scanty  or  moderate 
diet,  is  sure  to  diminish  the  amount  of  fat.  Temperament  also 
exerts  a  powerful  influence  upon  corpulency,  and  so  do  the  states 
of  feeling  and  the  conditions  of  the  mind.  In  diseases  of  a 
wasting  character,  and  under  any  circumstances  which  interfere 
with  nutrition,  the  fat  is  much  diminished.  In  another  class  of 
diseases,  it  is  increased,  and  pathological  deposits  of  it  take 
place. 

It  is  undoubtedly  true  that  the  greater  portion  of  the  fat 
found  in  all  animals  is  taken  into  the  system  preformed.  In  the 
carnivorous  animals  it  occurs  in  abundance  in  their  food,  and  in 
others,  it  has  been  found  to  exist  in  sufficient  quantity  in  vege- 
tables, to  supply  all  that  they  contain.  It  is,  however,  also  true 
that  animals  possess  the  power  of  forming  it  within  their  bodies 
from  food  which  does  not  contain  it,  though  where,  when,  or  how 
this  is  done,  has  never  yet  been  satisfactorily  determined. 


NON-NITROGENOUS  BASES  AND  SALTS — HALOIDS.  93 

The  uses  of  fat  in  tlie  animal  body  are  very  numerous.  Its 
beautifying  property,  the  softness  it  communicates  to  the  form, 
the  agreeable  plumpness,  and  exquisite  flowing  contour  which 
result  from  it,  will  be  best  appreciated  by  comparing  a  young, 
graceful,  well-developed  woman  with  the  thin,  frail,  perishing 
victim  of  consumption ;  or  the  plump,  crowing,  well-fed  baby, 
with  the  poor  emaciated  little  sufferer,  that  has  been  worn  away 
with  cholera  infantum  or  marasmus.  "How  different,"  says 
Lehmann,  "  would  be  the  appearance  of  the  face,  if  all  the  fat 
were  removed  from  the  muscles,  and  from  below  the  skin.  The 
fat  which  smooths  the  bony  corners  and  angles,  and  the  narrow 
muscles  of  the  face,  is  the  cosmetic  employed  by  nature  to  stamp 
the  human  countenance  with  the  incomparable  impress  which 
exalts  it  far  above  all  other  animals." 

Fat  is  also  useful  in  equalizing  pressure  upon  the  external 
parts  of  the  body ;  and  we  find,  therefore,  that  it  is  deposited  in 
greater  abundance  in  those  parts  which  are  most  subject  to  pres- 
sure, as  the  soles  of  the  feet,  and  the  buttocks.  It  also  dimi- 
nishes friction,  and  allows  the  muscles  to  glide  over  each  other 
with  facility. 

When  fluid,  fat  is  a  bad  conductor  of  heat.  Its  diffusion, 
therefore,  over  the  surface  of  the  body,  must  afford  a  protection 
to  the  system  from  the  extremes  of  temperature  to  which  we 
are  subjected. 

.  Liebig  has  shown  that  fat  subserves  another  important  purpose 
in  the  economy,  the  maintenance  of  animal  heat.  Lehmann 
regards  it  as  one  of  the  most  active  agents  in  the  metamorphosis 
of  animal  matter.  He  found  a  small  quantity  of  it  to  be  indis- 
pensable to  the  solution  of  nitrogenous  articles  of  food  during 
the  process  of  gastric  digestion.  Still  farther,  it  may  now  be 
regarded  as  a  settled  fact,  that  fat  is  the  basis  of  organization, 
because  the  granules  which  lie  at  the  foundation  of  all  cell- 
metamorphosis,  are  themselves  formed  by  the  coagulation  of 
albumen  around  globules  of  fat.  Fat  is  also  supposed  to  co- 
operate in  the  formation  of  the  blood  pigment. 

The  bile  is  formed  in  part  from  the  fats  of  the  body,  and  of 
the  food.  In  the  yolk-sac  of  the  egg,  it  is  well  known  that  the 
fat  of  the  yolk  is  in  part  converted  into  bile,  to  such  an  extent, 


94  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

that  the  alcoholic  extract  of  the  entire  yolk  contains  enough  to 
be  recognized  by  Pettenkofer's  test.  The  blood  of  the  portal 
vein,  however,  contains  more  fat  than  that  of  any  other  vein  in 
the. body,  and  this  fat  differs  from  the  ordinary  fat  of  the  blood 
in  being  of  a  dark  brown  color,  and  very  rich  in  olein. 

"When  animals  are  starved  for  any  length  of  time,  it  is  well 
known  that  they  rapidly  become  emaciated ;  the  urine  still  ex- 
hibits nitrogenous  constituents,  corresponding  in  amount  to  the 
products  of  effete  tissue,  while  the  gall-bladder  is  perfectly  full, 
and  the  liver  constantly  pours  out  bile  into  the  intestine,  as  I 
have  convinced  myself  by  a  repetition  of  Magendie's  experi- 
ments. The  above  fact  seems  to  explain  the  cause  of  the  bitter 
taste  of  which  persons  suffering  from  starvation  very  frequently 
complain.  Whence  can  the  liver  extract  the  materials  necessary 
to  the  formation  of  bile  ?  The  urine,  although  poorer  in  solid 
constituents,  always  contains  a  considerable  quantity  of  urea ; 
and  the  animal  body  contains  few  or  no  highly  carbonaceous 
substances,  with  the  exception  of  fat,  which  we  here  observe 
disappearing  very  rapidly,  while  at  the  same  time  there  is  an 
abundant  secretion  of  bile. 

"  In  disease,  the  diminution  or  increase  of  fat  is  inversely  pro- 
portional to  the  secretion  of  bile.  Polycholia,  which  seldom 
occurs  in  adults,  but  which,  in  children,  constitutes  the  affection 
known  as  Icterus  neonatorum,  is  always  accompanied  with  rapid 
emaciation.  In  acute  diseases,  emaciation  generally  occurs  in 
conjunction  with  critical  symptoms,  that  is  to  say,  when  the 
organs  of  excretion  resume  their  activity,  and  eliminate  the 
materials  that  have  become  effete ;  hence  the  copious  semi-solid 
feces.  In  all  acute  or  chronic  diseases  of  the  liver,  the  fat  ac- 
cumulates either  merely  in  the  blood,  or  in  the  blood  and  in  the 
cellular  tissue.  The  obesity  observed  in  habitual  drunkards  is 
not  in  consequence  of  their  taking  too  much  combustible  into 
their  bodies  (brandy-drinkers,  moreover,  generally  take  only 
small  quantities  of  solid  food),  but  in  consequence  of  the  dis- 
turbed hepatic  action,  which  the  invariably  abnormal  condition 
of  the  liver,  found  after  death,  in  these  cases,  proves  to  have 
existed."*     Besides  these  facts,  it  has  been  found  that  in  inflam- 

*  Lehmana's  Physiological  Chemistry,  vol.  i.  p.  271. 


NON-NITROGENOUS  BASES  AND  SALTS — ^^HALOIDS.  95 

mation  of  the  liver,  and  indeed  in  any  disease  in  -which  its 
functions  are  suspended,  the  fat  in  the  blood  is  more  increased 
than  in  any  other  class  of  diseases. 

The  hydrated  oxide  of  cetyl^  C32H33O.HO,  the  basis  of  sperma- 
ceti, occurs  only  in  that  fat ;  and,  therefore,  requires  no  special 
notice  here. 

LIPOIDS. 

Under  this  head  are  classified  the  non-saponifiable  fats. 

CHOLESTERIN. 

This  body  separates  from  its  hot  alcoholic  solutions  in  pearly 
scales,  which  appear  under  the  microscope  as  thin  rhombic  ta- 
blets. It  fuses  at  29G°,  solidifying  again  in  a  crystalline  form  at 
^QQ°.  It  becomes  electrical  by  friction, 'is  insoluble  in  water, 
but    soluble   in   nine   parts   of  -p.     yj 

boiling  alcohol,  in  soap-water, 
in  the  fatty  oils,  and  in  tauro- 
cholic  acid.  It  is  converted, 
by  boiling  with  nitric  acid,  into 
a  resinous  mass  and  then  into 
caproic,  acetic,  butyric,  oxalic, 
and  cholesteric  acids.  On  dry 
distillation,  it  leaves  a  char- 
coal, and  sends  over  an  oily  substance  of  a  geranium  odor. 

Its  formula  is  C37H32O.  The  products  of  its  decomposition 
are  three  cholesterilines  and  two  cholesterones. 

It  is  best  prepared  by  dissolving  gall-stones  containing  it  in 
boiling  alcohol,  filtering  while  hot,  and  purifying  by  repeated 
crystallizations  from  hot  alcohol. 

Small  quantities  of  it  are  found  in  most  of  the  animal  fluids. 
It  was  first  found  in  biliary  calculi,  and  has  since  been  disco- 
vered to  be  a  normal  constituent  of  all  bile.  It  has  also  been 
found  in  the  blood,  in  the  brain,  in  pus,  in  the  solid  excrements, 
and  in  many  products  of  disease. 

Its  origin  is  unknown.  It  must  be  formed  in  the  living  body, 
because  it  does  not  exist  in  the  vegetable  kingdom. 


Cliolesterin. 


96  PRINCIPLES  OP  ANIMAL  CHEMISTRY. 


SEROLIN. 

This  substance  was  obtained  by  Bouclet  by  extracting  with 
hot  alcohol  blood  which  had  been  dried,  boiled  with  water,  and 
again  dried.  As  the  alcohol  cooled,  the  serolin  separated  in 
pearly,  glistening  flocculi,  slightly  soluble  in  cold,  freely  in  hot 
alcohol  and  in  water.     It  contains  nitrogen. 

Of  castorin  and  amhrein,  we  shall  only  say  that  one  is  a  con- 
stituent of  castor,  the  other  of  amber. 


CHAPTER    IX. 

NON-NITROGENOUS  NEUTRAL  BODIES. 

Most  of  these  substances  closely  resemble  one  another  in 
their  empirical  constitution,  whence  many  of  them  have  received 
a  common  title,  "carbo-hydrates"  or  hydro-carbons.  Their  oxy- 
gen and  hydrogen  are  combined  in  the  same  ratio  as  in  water, 
and  the  number  of  their  atoms  of  carbon  is  divisible  by  6. 

GLUCOSE. 

This  substance,  the  grape-sugar  of  the  French  chemists,  is 
identical  with  diabetic  sugar.  It  crystallizes  in  warty  masses 
of  minute  rhombic  plates.  It  is  white,  inodorous,  sweeter  than 
milk-sugar,  not  so  sweet  as  cane-sugar;  soluble  in  water,  and 
slightly  so  in  alcohol ;  insoluble  in  ether.  Its  aqueous  solution 
turns  a  polarized  ray  of  light  to  the  right.  It  melts  at  212°,  and 
at  284°  becomes  converted  into  caramel,  developing  a  sweetish 
odor.     At  a  higher  heat,  it  is  charred. 

In  contact  with  nitrogenous  bodies,  it  passes  into  lactic  and 
butyric  acids.  With  yeast,  it  ferments  into  alcohol.  Nitric 
acid  converts  it  into  oxalic  and  saccharic  acids ;  sulphuric  acid 
browns  it,  but  not  so  fast  as  it  does  cane-sugar ;  potash,  boiled 
with  it,  gives  it  a  fine  brownish-red  tint.  Treated  with  caustic 
potash,  and  then  with  sulphate  of  copper,  a  blue  solution  is 


NON-NITROGENOUS  NEUTRAL  BODIES.  97 

formed,  M-liich  gradually  turns  green  and  deposits  a  red  pow- 
der. It  forms  a  beautiful  crystalline  compound  with  chloride  of 
sodium. 

Its  formula  is  C^JI^^O^^. 

It  is  widely  diffused  through  the  vegetable  kingdom,  and  may 
be  prepared  by  the  action  of  acids  on  other  sugars,  starch, 
woody  fibre,  kc.  The  ordinary  method  of  obtaining  it  from  dia- 
betic urine  is  liable  to  the  objection  that  it  leaves  acetates  min- 
gled with  the  sugar.  Lehmann's  plan  is  to  evaporate  it  care- 
fully till  the  whole  residue  is  converted  into  a  solid,  yellowish- 
white  mass,  which  is  extracted  first  with  absolute  alcohol  and 
then  with  hot  spirit.  From  the  latter,  it  is  allowed  to  crystal- 
lize, and  the  mother-liquid  is  evaporated  to  facilitate  farther 
crystallization. 

Even  this  method,  however,  according  to  Lehmann,  does  not 
furnish  this  substance  in  a  chemically  pure  state.  To  procure 
it  totally  uncontaminated  by  foreign  ingredients,  he  saturates 
the  aqueous  solution  of  the  alcoholic  extract  with  chloride  of 
sodium,  crystallizes,  dissolves  the  crystals  in  water,  and  cau- 
tiously precipitates  with  sulphate  of  silver.  He  evaporates  the 
filtered  fluid,  extracts  with  alcohol,  and  crystallizes  from  dis- 
tilled water. 

The  tests  for  glucose  are  fermentation,  Trommer's  test,  polar- 
ization, and  several  others  which  the  progress  of  science  has 
shown  to  be  totally  untrustworthy. 

Trommer's  test  is  the  reaction  with  potash  and  sulphate  of 
copper.  To  employ  it,  the  fluid  is  treated  with  caustic  jjotash, 
filtered  if  necessary,  it  being  understood  that  excess  of  potash 
does  no  harm,  and  then  charged  with  a  dilute  solution  of  sul- 
2)Jiate  of  coiyper,  very  gradually  and  carefully  added  to  it.  A 
precipitate  usually  falls,  which  is  dissolved  on  stirring  the  fluid. 
After  standing  awhile,  a  pure  red  or  yellow  precipitate  is  formed. 
If  the  mixture  be  boiled,  as  commonly  recommended,  the  color 
is  not  so  fine ;  and,  besides  that,  other  substances  also  throw 
down  the  suboxide  of  copper  when  aided  by  heat,  which  do  not 
effect  this  change  when  kept  at  the  common  temperature. 

If  but  little  sugar  be  present,  it  is  best  to  evaporate  to  dry- 
ness, to  extract  with  alcohol,  and  to  apply  the  test  to  the  watery 
7 


98  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 

solution  of  the  alcoholic  extract.  In  searching  for  sugar  in 
albuminous  fluids,  we  must  first  neutralize  with  acetic  acid,  then 
evaporate,  then  extract  with  alcohol,  precipitate  the  sugar  by 
an  alcoholic  solution  of  potash,  dissolve  the  precipitate  in  water, 
and  apply  the  sulphate  of  copper  to  this  solution.  In  this  man- 
ner, the  most  minute  portion  of  sugar  will  give  a  very  distinct 
reaction. 

The  fermentation  test  is  applied  by  adding  yeast  to  a  solution 
of  glucose ;  carbonic  acid  is  evolved,  alcohol  is  formed,  and  the 
torula  cerevisice,  a  microscopic  fungus,  makes  its  appearance  in 
the  fluid.  It  requires  much  familiarity  with  the  microscope 
properly  to  apply  this  test ;  for  urine,  which  contains  no  sugar, 
develops  a  fungus  of  the  same  form,  difi"ering  only  from  the 
torula  in  size. 

Fehling  has  applied  Trommer's  test  to  the  quantitative  deter- 
mination of  sugar.  As  modified  by  Dr.  Day,  his  test  solution 
is  prepared  as  follows:  Dissolve  69  grains  of  crystallized  sul- 
phate of  copper  in  five  times  their  weight  of  distilled  water,  and 
add  to  it  first,  a  concentrated  solution  of  268  grains  of  tartrate 
of  potash  and  then  a  solution  of  80  grains  of  hydrate  of  soda  in 
an  ounce  of  distilled  water.  Put  the  solution  into  an  alkalime- 
ter  tube,  and  add  distilled  water  to  make  1000  grain-measures 
of  liquid.  Every  100  grain-measures  of  this  fluid  is  equivalent 
to  1  grain  of  grape-sugar. 

For  clinical  purposes,  the  fermentation  test  gives  sufiiciently 
accurate  results.  The  urine  is  weighed,  and  allowed  to  ferment 
at  99°  in  a  Fresenius's  alkalimetrical  apparatus.  After  forty- 
eight  hours,  the  whole  is  weighed,  and  the  carbonic  acid  evolved 
estimated  by  the  loss  of  weight. 

Sugar  is  always  found  in  the  intestines  after  the  use  of  vege- 
table food.  It  is  found  in  the  chyle,  seldom  in  the  hloocl,  con- 
stantly in  eggs  and  in  the  tissue  of  the  liver.  In  the  urine  and 
in  most  of  the  fluids,  it  is  found  in  diabetes. 

Glucose  originates  from  the  digestion  of  amylaceous  sub- 
stances, and  also,  it  is  believed,  from  the  metamorphosis  of 
the  protein  compounds.  Bernard  finds  that  the  liver  can  al- 
ways be  made  to  secrete  in  great  quantities  when  the  medulla 
oblongata,  on  the  floor  of  the  fourth  ventricle,  is  irritated.     It 


NON-NITROGENOUS  NEUTRAL  BODIES.  99 

has  also  been  formed  in  undue  quantities  when  respiration  has 
been  interfered  with.  Its  use  appears  to  be  to  act  as  a  pabu- 
lum to  the  processes  of  oxidation  which  originate  and  keep  up 
the  animal  heat.  That  this  change  is  effected  in  the  blood 
appears  certain;  and  it  is  probable  that  the  sugar  is  first  con- 
verted into  an  acid,  which  unites  with  the  alkali  of  that  fluid  and 
becomes  a  carbonate  of  the  alkali,  so  evolving  heat. 

MILK-SUGAR. 

Milk-sugar  crystallizes  in  white  opaque  prisms  or  rhombohedra, 
containing  two  atoms  of  water.  It  is  hard,  craunches  between 
the  teeth;  has  a  faint  sweetness;  is  inodorous,  soluble  in  water, 
insoluble  in  absolute  alcohol  and  ether,  and  its  aqueous  solu- 
tion turns  the  polarized  ray  to  the  right.  Dilute  sulphuric,  hydro- 
chloric, acetic,  and  citric  acids  convert  it  into  glucose.  Nitric 
acid  changes  it  into  mucic  acid,  with  a  little  oxalic,  saccharic, 
and  carbonic  acid ;  chromic  acid  produces  from  it  both  formic 
acid  and  aldehyde.  It  reacts  with  sulphate  of  copper  and  pot- 
ash like  glucose,  and  ferments,  but  not  so  readily  as  other 
sugars. 

Crystallized,  it  has  the  same  composition  as  anhydrous  glu- 
cose; but,  when  heated,  it  loses  water,  and  becomes  CigHgOg. 

It  is  usually  obtained  by  evaporating  whey,  and  letting  it  stand 
a  long  time  in  a  cool  place  to  crystallize.  The  crystals  are 
purified  by  recrystallization.  Haidlen  boils  milk  with  one- 
eighth  its  weight  of  sulphate  of  lime,  which  coagulates  the 
casein,  filters,  evaporates  to  dryness,  removes  the  fat  with  ether, 
and  extracts  the  sugar  with  boiling  alcohol. 

It  is  distinguished  from  glucose  by  the  difficulty  with  which 
it  dissolves  in  alcohol,  the  slowness  of  its  fermentation  in  the 
presence  of  yeast,  and  its  convertibility  into  mucic  acid  by  the 
action  of  nitric  acid. 

It  is  determined  quantitatively  by  Haidlen's  process,  just 
given ;  or,  when  more  accuracy  is  required,  by  using  Fehling's 
test  on  the  alcoholic  extract  thus  obtained. 

This  sugar  is  found  in  the  milk  of  all  mammalia.  In  woman's 
milk,  its  amount  ranges  from  3.2  to  6.245,  in  cow's  milk,  it  has 


100  PKINCIPLES  OF  ANIMAL  CHEMISTRY. 

been  usually  stated  to  average  from  3.4  to  4.3g,  but  Lehmann 
finds  this  too  low.  In  asses'  milk,  it  is  rated  at  4.5g ;  in  mares', 
at  8.7§ ;  in  goat's,  at  4.4g.  In  the  colostrum,  Simon  found  7^,  and 
in  the  milk  six  days  after  delivery  only  6,241).  As  nursing  goes 
on,  it  continually  diminishes,  and  neither  abundance  nor  insuffi- 
ciency of  diet  nor  disease  affects  its  quantity.  Braconnot  claims 
to  have  found  it  in  the  cotyledons  of  the  seeds  of  plants. 

Dumas  and  Bensch  have  shown  that  its  quantity  is  increased 
by  a  vegetable  diet,  so  that  it  is  probably  formed  from  the  glu- 
cose resulting  from  the  metamorphosis  of  starch,  though  when 
or  how  has  never  been  determined. 

The  milk-sugar  subserves  in  the  infant  organism  the  same 
purposes  as  starch  and  the  other  carbo-hydrates  in  the  adult. 


CHAPTER    X 

PIGMENTS. 


Nothing  definite  is  known  of  animal  pigments,  so  that  they 
are  classified  according  to  color. 

HiEMATIN. 

This  is  usually  regarded  as  the  red  pigment  of  the  corpuscles, 
but  it  is  unknown  whether  it  is  a  product  of  metamorphosis  of 
the  true  coloring  matter  of  the  blood,  or  whether  we  obtain  it 
coagulated.  Neither  has  it  ever  been  isolated,  in  its  soluble  state, 
from  the  globulin.  As  obtained,  it  is  a  dark-brown,  slightly 
lustrous,  tasteless,  inodorous  mass ;  insoluble  in  water,  alcohol, 
ether,  or  oils.  It  dissolves,  however,  in  alcohol  acidulated 
with  sulphuric  or  hydrochloric  acid,  but  not  in  water  similarly 
prepared.  The  concentrated  acids  do  not  dissolve  it,  but  only 
take  up  a  little  of  its  iron.  The  alkalies,  however,  dissolve  it 
readily. 

Digested  in  chlorine  water,  the  iron  dissolves  as  perchloride 


PIGMENTS.  101 

of  iron,  and  wliite  flocculi  fall,  which  Mulder  regards  as  a  com- 
bination of  chlorous  acid  and  hsematin  free  from  iron.  Concen- 
trated sulphuric  acid  deprives  it  of  its  iron,  buf  does  not  affect 
its  color  nor  alter  its  elementary  composition. 

Mulder's  formula  is  C44H22N30QFe.  The  manner  in  which 
the  iron  is  combined  with  the  hfematin  is  still  unknown,  not- 
withstanding the  numerous  hypotheses  with  which  we  have  been 
favored.  It  has,  however,  been  clearly  proved  not  to  be  essen- 
tial to  the  color  of  the  hcematin. 

H^matin  is  obtained  by  treating  blood  with  eight  times  its 
volume  of  a  solution  of  sulphate  of  soda  or  of  chloride  of  sodium, 
filtering  and  washing  with  the  same  solution.  The  residue  is 
then  dissolved  in  water  and  coagulated  by  heat.  The  coagulum 
is  washed,  dried,  finely  triturated,  and  boiled  with  alcohol  acidu- 
lated with  sulphuric  acid,  till  the  fluid  passes  through  decolor- 
ized. It  is  now  saturated  with  ammonia,  when  it  deposits  sul- 
phate of  ammonia  and  globulin.  These  are  removed  by  filtra- 
tion, the  fluid  evaporated  to  dryness,  the  solid  residue  extracted 
with  water,  alcohol,  and  ether,  and  again  dissolved  in  alcohol 
saturated  with  ammonia.  The  solution  is  filtered,  evaporated, 
and  the  residue  extracted  with  water. 

Hsematoidin  is  a  modified  hajmatin  found  in  certain  extrava- 
sations of  blood.  It  occurs  in  granules,  globules,  and  jagged 
masses,  as  well  as  in  crystals,  presenting  the  form  of  oblique 
rhombic  prisms. 

Hitherto,  haematin  has  only  been  found  in  the  blood-corpuscles 
of  the  higher  animals,  in  which  it  occurs  as  a  viscid  solution, 
mixed  with  globulin.  The  proportion  of  haematin  in  the  cor- 
puscles has  been  calculated  at  5.72^,  in  the  blood  at  0.718^. 

The  origin  of  haematin  is  unknown.  It  is  found  in  the  tho- 
racic duct,  and  has  been  supposed  to  be  formed  from  the  fat. 

The  function  of  haematin  is  equally  obscure.  While  one  set 
of  experiments  seem  to  show  that  it  has  an  important  relation 
to  the  aeration  of  the  blood,  others  are  equally  pointed  in  favor 
of  an  opposite  hypothesis.  Yirchow  has  shown  that,  during  its 
decomposition,  it  passes  into  substances  similar  to  if  not  identical 
with  melanin  and  bile  pigment. 


102  PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


MELANIN. 

Melanin  is  obtained  as  a  black,  inodorous,  tasteless  mass  or 
powder;  insoluble  in  water,  alcohol,  ether,  or  acids,  soluble  in 
dilute  solution  of  potash,  from  which  it  may  be  precipitated  by 
hydrochloric  acid.  Nitric  acid  decomposes  it,  but  chlorine  does 
not.  It  conducts  electricity,  does  not  fuse,  but  burns  in  the  air, 
leaving  a  yellowish  ash,  containing  chloride  of  sodium,  bone- 
earth,  and  peroxide  of  iron. 

Scherer  publishes,  as  the  mean  of  three  analyses,  the  follow- 
ing:— 

Carbon 58.084 

Hydrogen          ....  5.917 

Nitrogen 13.768 

Oxygen     .....  22.231 

100.000 

The  best  method  of  obtaining  it  is  by  inclosing  the  choroid 
coat  of  the  eye  in  a  clean  rag,  and  washing  out  the  coloring 
matter. 

Whether  the  black  pigments,  obtained  from  parts  ojf  the  body 
other  than  the  choroid  coat  of  the  eye,  are  identical  with  mela- 
nin, it  is  impossible  to  say  at  present.  It  is  probably  formed 
from  hsematin. 

BILE  PIGMENT. 

There  are  two  distinct  modifications  of  the  biliary  pigment, 
which,  however,  under  certain  circumstances,  seem  capable  of 
passing  into  one  another.  One  of  these,  the  brown  ijigme^it, 
the  choU'pyrrMn  of  Berzelius  and  the  hiliphoein  of  Simon,  occurs 
as  a  reddish-brown,  non-crystalline  powder;  inodorous  and  taste- 
less ;  insoluble  in  water,  slightly  soluble  in  ether,  but  more  so  in 
alcohol,  to  which  it  communicates  a  yellow  tint ;  forming  with 
caustic  alkalies  a  clear  yellow  solution  which  soon  changes  to 
greenish-brown.  The  yellow  solution,  when  treated  with  nitric 
acid,  passes  through  the  various  tints  of  green,  blue,  violet,  red, 


PIGMENTS.  103 

and  yellow  again.  Hydrochloric  acid  throws  down  from  the 
potash  solution  a  green  precipitate,  which  seems  to  be  identical 
with  the  green  modification.  Acids  make  it  green,  and  chlorine 
bleaches  it.  It  combines  bases  ;  and  its  combinations  with  the 
alkaline  earths  are  insoluble. 

The  green  pigment,  the  hiliverdin  of  Berzelius,  is  insoluble  in 
water,  slightly  soluble  in  alcohol,  form- 
ing with  ether  a  red  solution,  soluble 
in  fats,  in  hydrochloric  and  sulphuric 
acids  with  a  green  color,  and  in  acetic 
acid  and  the  alkalies  with  a  yellowish- 
red  tint.  Berzelius  regards  it  as  iden- 
tical with  the  chloropyil  of  leaves.  It 
is  decomposed  with  extreme  facility. 

Berzelius  also  found  in  bile  some 
reddish-yellow  crystals,  to  which  he 
gave  the  name  hilifulvin. 

Its  composition  has  not  been  settled.  From  7  to  9^  of  nitro- 
gen has  been  found  in  it. 

Nitric  acid  is  the  usual  test  for  it.  When  it  exists  in  small 
quantities,  it  is  precipitated  with  basic  acetate  of  lead,  and  dis- 
solved in  alcohol,  or  diluted  with  sulphuric  acid,  to  which  it 
communicates  a  green  tinge. 

This  pigment  is  found  usually  dissolved,  though  often  only 
suspended  in  the  bile.  In  the  intestines  it  is  very  rapidly  modi- 
fied. The  green  tint  seen  in  the  excrements  is  very  often  de- 
composed blood  instead  of  modified  bile.  In  disease,  it  may  be 
found  in  most  of  the  solids  and  fluids  of  the  body. 

Its  use  in  the  body  is  unknown.  Its  origin  is  also  obscure, 
though  facts  seem  to  point  to  hoematin  as  its  source  ;  at  any  rate, 
recent  observations  appear  to  show  that  it  is  not  formed  in  the 
liver. 

URINE  PIGMENT. 

Of  this  but  little  is  known,  owing  to  its  extreme  proneness  to 
decomposition.  Heller  enumerates  three  pigments,  uroxanthin, 
uroglaucin,  and  urrhodin. 


104 


PRINCIPLES  OF  ANIMAL  CHEMISTRY. 


Fig.  19. 


JJroxantliin  is  a  yellow  pigment,  which  exists  in  solution  in 
healthy  urine  and  gives  it  its  yellow  color.  It  may  be  oxidized 
into  uroojlaucin  and  urrhodin. 

Uroglaucin  is  a  dark  blue  powder,  which,  when  dried,  has  a 
coppery  lustre,  like  indigo,  and  dis- 
solves in  alcohol  with  a  fine  purple 
color.  It  crystallizes  in  groups  which 
are  nearly  black,  but  are  blue  and 
transparent  at  the  edges. 

Urrhodin  occurs  in  larger  quantity 
than  uroglaucin.  It  occurs  in  gra- 
nules, which,  under  the  microscope, 
have  a  fine  rose-color.  It  is  resinous, 
and  burns  with  a  clear  flame. 

Uroerytlirin  is  the  red  coloring 
matter  which  appears  in  the  urine  in 
intermittent  fever  and  some  inflammations.  It  is  a  scarlet 
powder,  inodorous,  and  almost  tasteless ;  soluble  with  a  faintly 
acid  reaction  in  water  and  spirit. 

In  addition  to  these  substances,  a  crowd  of  unexamined  and 
unknown  products  are  classified  by  chemists  under  the  head  of 
extractive  matters.  When  this  phrase  is  used,  all  that  is  meant 
by  it  is,  that  after  the  organic  matters  already  described,  and 
the  various  inorganic  salts,  have  been  removed  from  the  tissues  or 
fluids  examined,  there  still  remain  certain  nameless,  unstudied 
bodies,  which  are  soluble  either  in  water,  dilute  alcohol,  or  abso- 
lute alcohol.  They  are  divided  into  water- extractive,  spirit-ex- 
tractive, and  alcohol-extractive,  according  to  their  behavior  with 
the  three  above-named  reagents. 


Uroglaucin. 


EOOK  II. 

DIGESTION. 


CHAPTEE  I. 

PHYSIOLOGICAL  KELATIONS  OF  DIGESTION. 

It  has  already  been  said  that,  in  examining  the  functions  of 
the  human  body,  we  must  necessarily  proceed  in  a  circle.  They 
are  all  so  completely  dependent  upon  one  another,  the  last  re- 
sult of  one  being  the  basis  of  the  operations  of  another,  that  no 
satisfactory  view  can  be  obtained  of  any  one  of  them,  until  the 
student  have  attained  some  general  idea  of  the  whole. 

If,  for  example,  we  commence  the  study  of  the  intellectual 
functions  of  man,  we  find  it  impossible  to  get  any  adequate 
notion  of  them  by  a  mere  subjective  examination.  The  man 
who  attempts  to  comprehend  his  mental  acts  by  intellectual  in- 
trospection alone,  will  be  grievously  at  fault,  because  we  know 
■nothing  of  our  spirits  independent  of  the  matter  to  which  they 
are  tied.  The  slightest  changes  in  this,  produce  the  greatest 
irregularities  in  them.  The  mind  may  be  in  a  state  of  the 
highest  activity,  giving  birth  to  the  profoundest  thoughts,  and 
the  most  brilliant  images,  descending  upon  the  sublimest  ideas, 
and  grappling  with  the  loftiest  themes ;  but,  let  a  few  drops  of 
blood  spirt  out  upon  the  delicate  tissue  of  the  brain,  and  all  is 
over.  The  bright  eye  ceases  to  sparkle,  the  eloquent  tongue  to 
speak,  and  all  that  mental  power  that  we  have  so  much  admired 
is  as  completely  annihilated  as  though  the  mind  itself  had  ceased 
to  exist.  A  little  lymph,  effused  upon  the  brain  of  an  intelligent 
child,  makes  an  idiot  of  him.     A  blow,  which  induces  changes 


106  DIGESTION. 

not  to  be  disclosed  by  the  scalpel,  the  microscope,  the  test-glass, 
or  any  of  our  most  refined  and  delicate  modes  of  investigation, 
converts  the  gentleman  into  a  ruffian,  the  saint  into  a  reprobate, 
and  the  prude  into  a  prostitute. 

It  is  too  late  for  the  pure  metaphysician  to  attempt  to  escape 
the  force  of  these  facts,  by  the  assertion  that  the  mind  retains 
all  its  native  force  and  activity,  but  that  the  shattered  and 
ruined  organs  refuse  to  permit  its  manifestation.  The  day  for 
assumptions  and  assertions  has  gone  by,  and  the  world  demands 
proof  instead  of  a  bare  zpse  dixit.  Such  an  unphilosophical 
wrenching  of  facts  to  fit  a  theory  can  no  longer  be  permitted ; 
and  the  more  modest  confession,  that  the  Almighty  maker  has 
seen  fit  to  yoke  intellectual  faculties  and  material  organs  in  a 
manner  as  yet  inscrutable  to  us,  is  at  once  nearer  the  truth, 
more  appropriate  in  view  of  our  immeasurable  ignorance,  and 
better  adapted  to  promote  the  advance  of  science,  which  is,  and 
always  has  been  impeded  by  these  stumbling-blocks  of  theories, 
that  have  been  thrown  in  her  way  by  her  well-intentioned 
votaries. 

The  student  of  mental  philosophy,  thus  driven  to  consider  the 
physical  framework  of  man,  discovers  that  the  mind  and  the 
body  act  and  react  upon  one  another  in  the  most  remarkable 
manner.  He  finds,  on  the  one  hand,  that  bodily  states  influ- 
ence mental  operations,  and  that  the  intellect  and  the  feelings 
powerfully  modify  the  functions  of  the  body.  Thus,  a  small 
amount  of  alcohol  taken  into  the  stomach  brutalizes  a  man,  and 
a  suspension  of  the  secretion  of  his  liver  or  kidneys  stupefies 
him  completely,  and  suspends  all  his  mental  acts.  On  the  other 
hand,  a  fit  of  rage  gives  him  the  jaundice,  because  this  passion 
influences  the  secretion  of  the  liver;  grief  arrests  his  digestion; 
fear  depresses,  hope  stimulates  his  circulation,  and  mental  anx- 
iety impairs  his  nutrition  and  emaciates  him.  Thus  the  mind 
influences  those  functions  which  seem  to  be  entirely  withdrawn 
from  its  control. 

If  such  close  relations,  therefore,  subsist  between  the  mind 
and  the  body,  much  more  shall  we  expect  to  find  the  difi'erent 
functions  of  the  body  itself  intimately  connected  with  one 
another. 


PHYSIOLOGICAL  RELATIONS  OF  DIGESTION.  107 

In  considering  this  interdependence,  it  is  difficult  to  fix  upon 
a  starting-point,  because  so  many  present  themselves.  If  we 
inquire,  however,  what  the  ultimate  object  of  human  existence 
is,  we  shall  have  a  very  natural  point  of  departure.  No  one 
will  answer  this  question  in  any  other  way  than  by  saying  that 
man  was  designed  to  go  on  improving  those  distinctive  faculties 
and  powers,  which  place  him  at  the  head  of  animated  nature. 
For  this  purpose  he  is  endowed  with  the  most  exquisitely  organ- 
ized nervous  system,  and  the  most  delicate  apparatus  of  sensa- 
tion. He  is  also  furnished  with  a  muscular  system,  capable  of 
supplying  all  his  common  animal  wants,  and  of  aiding  greatly  in 
the  development  of  his  intellectual  faculties.  Thus,  by  those 
two  modifications  of  common  locomotive  organs,  the  hand,  and 
the  apparatus  of  speech,  he  has  acquired  a  capacity  for  almost 
endless  improvement.  Take  them  away  from  him,  and  science, 
art,  indeed  all  mental  culture  would  be  simply  impossible  to  him. 

Physiologically,  then,  it  is  by  the  exercise  of  this  nervous 
and  muscular  apparatus  that  man  is  to  improve  his  intellectual 
powers.  But  we  are  so  constituted  that  exercise  is  productive 
of  waste.  Life  not  only  implies  and  involves  death,  but,  by  a 
strange  but  necessary  paradox,  it  is  death,  death  of  the  part 
which  exhibits  life.  Does  a  muscle  contract  ?  Its  little  disks 
die  by  myriads.  Does  a  nerve  thrill  with  sensation  ?  The 
nervous  matter  perishes,  and  we  find  its  wrecks  in  the  excretions. 
Does  the  brain  act  vigorously  ?  The  brain  too,  that  portion  of 
it,  at  least,  which  has  been  most  active,  dies  and  is  swept  away. 

Now,  it  must  be  manifest  that  there  must  be  some  counteract- 
ing agency,  or  we  should  very  soon  wear  ourselves  out.  This  is 
supplied  with  a  most  liberal  hand  by  nature.  Through  all  these 
active  organs  meander  countless  vessels,  which  carry  into  them 
the  fluid  from  which  the  shattered  tissues  are  to  be  repaired, 
and  others  which  convey  away  the  ruins  of  the  worn-out  organs, 
that  they  may  not  clog  the  wheels  of  life.  By  a  most  admirable 
provision  of  nature,  this  activity  which  is  so  destructive  becomes 
constructive  also.  The  rapid  changes  which  are  going  on  pro- 
duce an  increased  circulation  through  the  part.  Thus,  more 
new  matter  is  admitted,  and  the  old  is  more  rapidly  hurried 
away.     Life  is  too  strong  for  its  antagonist ;  and,  so  long  as  the 


108  DIGESTION. 

body  is  in  health,  the  formative  powers  exceed  the  disorgan- 
izing. This  we  know,  because  all  organs  increase  in  bulk  by 
exercise;  and  this  could  not  be  unless  more  matter  is  added  to 
them  by  blood  than  is  destroyed  by  their  activity. 

In  consequence  of  this  waste  which  is  perpetually  going  on, 
the  blood  that  is  returning  to  the  heart  must  necessarily  be 
clogged  with  many  impurities.  These,  if  allowed  to  remain, 
would  be  most  injurious  to  the  economy,  not  only  because  they 
would  by  their  presence  diminish  the  vitality  of  the  blood, 
but  because  also  they  must  act  as  direct  poisons  to  the  organs 
with  which  they  come  in  contact.  Plence,  an  apparatus  for  the 
elimination  of  this  effete  matter  must  be  provided.  The  various 
organs  of  secretion  supply  this  deficiency.  Excess  of  water  and 
nitrogenous  matters  are  carried  away  by  the  skin  and  the  kid- 
neys. Carbon  is  eliminated  by  the  liver  and  the  lungs,  and  the 
blood  is  thus  carefully  drained  of  its  numerous  impurities. 

But  even  this  is  not  sufficient.  Oxygen  must  be  introduced 
into  the  body,  for  the  whole  process  of  nutrition  and  elimination 
is,  among  other  changes,  a  gradual  oxidation.  Through  the 
lungs,  therefore,  and  in  part  through  the  skin,  this  introduction 
is  effected,  and  the  constant  chemical  action  between  this  atmo- 
spheric element  and  the  organic  contents  of  the  blood,  keeps  up 
the  animal  heat  which  is  essentially  necessary  to  the  due  per- 
formance of  the  different  functions  of  the  organism. 

It  is  manifest  that  in  all  these  changes,  the  body  is  ultimately 
a  loser.  Every  grain  extracted  and  appropriated  by  the  tissues 
is  a  grain  lost  by  the  blood.  Not  only  all  growth,  therefore, 
but  all  the  sustenance  of  the  body  must  come  from  without.  It 
is  introduced  as  food  into  the  stomach,  and  is  there  converted 
by  the  process  of  digestion  into  a  pulpy  mass,  which  becomes 
gradually  more  and  more  animalized  as  it  penetrates  the  eco- 
nomy. The  pultaceous  mass  which  enters  the  intestines  is  gra- 
dually changed  by  the  admixture  of  the  secretions  of  the  bowels 
and  their  accompanying  glands.  The  feculent  matter  is  sepa- 
rated from  that  which  is  nutritious,  and  this  is  gradually  vital- 
ized, and  removed  by  the  absorbents  and  bloodvessels.  The 
changes  still  go  on ;  granules,  globules,  and  cells  are  formed,  and 


PHYSIOLOGICAL  RELATIONS  OF  DIGESTION.  109 

the  new  matter,  thoroughly  fitted  for  the  uses  of  the  economy, 
mixes  with  the  blood  and  traverses  the  body. 

Thus,  all  the  functions  are  mutually  dependent.  Even  that 
which  is  properly  not  the  property  of  the  individual,  but  rather 
of  the  species,  the  great  function  of  reproduction,  is  not  exempt 
from  this  general  law  of  dependence.  The  phthisical  mother 
brings  forth  phthisical  children  ;  the  gouty  father  begets  a  gouty 
progeny.  Care  and  attention,  and  comfortable  circumstances 
for  a  series  of  generations  are  sure  to  produce  a  beautiful  and 
vigorous  race ;  while  poverty,  and  labor,  and  servitude  conjoined, 
and  continued  from  father  to  son,  certainly  engender  ugliness, 
deformity,  brutality,  and  disease.  No  one  can  doubt  this  who 
takes  the  trouble  to  compare  the  handsome  aristocracy  and  mid- 
dle classes  of  Ireland  with  the  extremely  ill-favored  peasantry 
of  that  unhappy  island. 

It  might  be  said  that  the  integrity  of  the  whole  body  de- 
pended upon  the  soundness  of  digestion,  but  this  would  convey 
an  erroneous  idea,  because  it  is  a  partial  truth.  The  soundness 
of  digestion  is  equally  dependent  upon  the  health  of  the  system. 
While  it  is  true  that  a  foul  stomach  engenders  headache  and 
fever,  it  is  equally  true  that  disorder  of  the  brain,  whether 
structural  or  functional,  or  only  a  mental  change,  interferes  with 
regular  and  healthy  digestion.  It  must  be  borne  in  mind,  there- 
fore, when  considering  the  influences  which  the  stomach  radiates 
outwards,  that  there  are  also  influences  radiating  from  every 
point  of  the  periphery  inwards  upon  it. 

It  is  impossible  to  do  more  than  glance  at  these  numerous 
relations  between  the  digestive  cavity  and  the  rest  of  the  organs. 
After  the  caveat  we  have  just  entered,  we  may  be  permitted  to 
say,  without  danger  of  being  misunderstood,  that  any  disturb- 
ance here  afi'ects  the  entire  economy.  The  process  of  digestion, 
being  that  agency  through  which  new  matter  is  introduced  into 
the  system  to  supply  the  place  of  that  which  is  wasted  and  car- 
ried ofi",  must,  if  materially  checked  or  arrested,  put  a  stop  to 
nutrition,  A  man,  though  fed  on  the  most  nutritious  food,  will 
starve  as  effectually  when,  from  any  cause,  digestion  is  pre- 
vented, as  though  all  food  was  taken  from  him. 

When  we  examine  the  relations  of  the  stomach  with  the  dif- 


110  DIGESTION. 

ferent  organs,  we  shall  find  that  besides  those  remarkable  chano-es 
which  it  induces  in  them,  and  which  have  received  the  name  of 
sympathies,  or  sympathetic  morbid  phenomena,  there  are  many 
other  conditions  of  these  remote  organs  which  are  dependent  on 
the  functional  activity  of  the  stomach. 

A  very  close  relation  subsists  between  the  great  functions  of 
digestion  and  respiration.  Much  of  the  food  which  we  take  is 
evidently  respiratory  ;  that  is,  it  is  plainly  designed  to  proceed 
in  the  current  of  the  blood  to  the  lungs,  there  to  be  oxidated, 
and  so  to  keep  up  the  animal  heat.  An  animal  will  starve  as 
speedily  when  this  sort  of  nutriment  is  taken  from  it,  as  when 
it  is  deprived  of  its  albuminous  aliment ;  and,  indeed,  it  appears 
that  the  reduction  of  temperature,  to  which  the  man  dying  by 
starvation  is  subjected,  constitutes  very  often  the  chief  element 
in  his  pathological  condition.  In  consequence  of  this  intimate 
relation,  irregularities  of  digestion  are  certainly  productive  of 
more  or  less  pulmonary  disturbance.  Dyspeptic  j^hthisis  is  not 
that  figment  of  the  imagination  which  some  physicians  profess 
to  believe  it,  but  a  sad  and  very  intelligible  reality.  There  are 
many  cases  of  tuberculous  disease,  which  the  watchful  and  ob- 
servant practitioner,  who  has  seen  the  case  from  the  beginning, 
knows  to  originate  in  (disordered  nutrition  commencing  with 
imperfect  digestion.  There  are  many  cases  also  in  which  an 
improvement  in  these  great  functions  of  nutrition  and  digestion 
has  without  doubt  arrested  the  progress  of  the  disease,  even  after 
it  had  committed  notable  havoc  in  the  lungs. 

The  relations  of  digestion  to  absorption,  sanguification,  and 
nutrition  are  too  manifest  to  demand  any  special  attention. 

The  influence  of  this  function  upon  the  circulation  is  also  very 
apparent.  When  it  goes  on  regularly  and  well,  the  vessels  are 
kept  in  that  state  of  moderate  fulness,  and  the  blood  in  that  due 
viscidity,  which  are  best  adapted  to  facilitate  the  transit  of  the 
nutritious  fluid.  Imperfections  in  the  digestive  process,  inde- 
pendently of  their  sympathetic  influence  upon  the  circulation, 
through  the  medium  of  the  nervous  system,  must  necessarily 
change  the  natural  consistence  of  the  blood,  and  consequently 
the  relations  between  it  and  the  apparatus  of  the  circulation,  and 
in  this  manner,  it  must  inevitably  interfere  with  that  function. 


FOOD.  '  111 

Its  influence  over  secretion  is  equally  well  known.  Unless  it 
supply  the  materials  for  the  secretions,  they  cannot  be  formed. 
Changes  in  digestion  are  sure  to  induce  changes  in  the  secre- 
tions. To  mention  but  a  single  example,  the  urine,  its  deposits, 
and  its  calculi  are  known  to  be  very  much  affected  liy  the  con- 
dition of  the  stomach,  so  that  medicaments  addressed  to  the 
latter  organ  will  certainly  affect  the  urinary  secretion. 

With  innervation,  locomotion,  and  reproduction,  aside  from 
the  general  influence  it  exerts  upon  them  through  the  medium 
of  the  function  of  nutrition,  and  by  sympathy,  its  connection  is 
not  distinctly  understood.  It  may  be  that  some  of  those  obscure 
changes,  which  we  now  call  sympathetic,  may  one  day  be  traced 
to  the  direct  chemical  agency  of  depraved  digestion. 


CHAPTER    II. 

FOOD. 

Fkom  Avhat  has  just  been  said  of  the  nature  of  the  process  of 
digestion,  it  is  manifest  that  the  food  must  contain  all  the  chemi- 
cal elements  which  enter  into  the  formation  of  the  tissues,  or  of 
the  secretions.  The  inorganic  substances,  the  soda,  the  potash, 
the  lime,  and  the  various  mineral  acids  must  come  in,  in  this 
alimentary  matter  which  we  daily  take  into  our  stomachs. 
These  materials  are  mixed  with  our  ordinary  food  in  sufiicient 
quantity,  and  are  disposed  of  by  the  system  as  fast  as  they  are 
introduced.  The  organic  matters  must  come  from  the  same 
source,  for  we  have  already  seen  that  the  animal  body  is  power- 
less to  produce  the  majority  of  them. 

That  these  organic  compounds  are  all  primarily  derived  from 
the  vegetable  kingdom,  is  manifest  from  what  has  already  been 
said.  In  the  human  body,  they  may  come  from  either  the  vege- 
table or  the  animal  food  we  eat.  Dr.  Front's  classification  of 
these  substances  being  very  convenient,  and  sanctioned,  more- 


112  DIGESTION. 

over,  by  tlie  high  authority  of  Carpenter,  •will  be  here  adopted, 
his  aqueous  group  being  omitted. 

The  first  group  is  the  saccharine,  the  members  of  which  con- 
tain hydrogen,  oxygen,  and  carbon  alone,  the  first  two  in  the 
proportion  to  form  water.  It  includes  not  only  the  sugars,  but 
all  those  vegetable  substances,  which,  having  an  analogous  com- 
position, may  be  converted  into  sugar.  As  we  have  already 
shown,  starch,  gum,  woody  fibre,  and  cellulose  possess  this  con- 
vertibility, and  are  therefore  ranked  with  saccharine  substances. 
Alcohol,  into  which  sugar  passes  after  fermentation,  being  a 
hydrated  oxide  of  ethyl,  is  a  haloid,  and  consequently  belongs 
to  the  next  group. 

The  oleaginous  group  includes  all  the  oils  and  fats  which  enter 
into  the  food.  Most,  if  not  all  of  these,  exist  preformed  in  the 
vegetable  kingdom  ;  though,  as  we  have  seen,  there  are  reasons 
for  believing  that  these  substances  may  be  formed  in  the  animal 
body  as  a  result  of  the  metamorphosis  of  tissue.  The  absence 
of  nitrogen,  the  abundance  of  hydrogen  and  carbon,  and  the 
small  quantity  of  oxygen  to  be  found  in  these  bodies,  are  their 
most  striking  characteristics. 

The  albuminous  group  is  sufiiciently  characterized  by  its  name. 
To  it  belong  all  the  protein  compounds  which  are  contained  in 
the  food.  The  composition  of  the  substances  contained  in  it 
has  already  been  described  with  sufficient  minuteness  under  the 
head  of  histogenetic  nitrogenous  bodies. 

The  gelatinous  group  consists  of  gelatine,  chondrin,  and  allied 
bodies,  and  is  derived  exclusively  from  the  animal  kingdom. 
There  are  a  few  alimentary  substances  which  cannot  be  classi- 
fied under  either  of  these  heads,  which  will  be  duly  noticed  as 
we  proceed. 

It  is  manifest  from  the  composition  of  the  sugars,  that  they 
cannot  subserve  directly  the  nutrition  of  the  body.  Either, 
therefore,  they  must  undergo  an  intermediate  metamorphosis, 
or  they  must  discharge  some  other  functions  in  the  economy. 
Liebig  has  done  very  much  for  the  philosophy  of  food  by  show- 
ing us  that,  while  one  portion  is  appropriated  to  the  production 
of  tissue,  another  passes  directly  into  the  blood  in  order  to 
undergo  oxidation,  and  consequently  to  generate  heat.      This 


FOOD.  113 

division  into  nutritious  and  respiratory  food  has  been  generally 
folloAved  by  physiologists,  and  seems  to  be  established  upon  the 
firm  foundation  of  fact. 

Among  the  respiratory  elements,  the  saccharine  group  stands 
prominent  because  of  the  quantity  of  carbon  and  hydrogen  it 
contains.  Those  members  ^  it  which  are  not  as  yet  sugars, 
are  converted  into  it  in  the  alimentary  canal,  while  the  sugars 
are  directly  taken  up  by  the  blood.  The  first  step  in  the  com- 
bustion, as  it  has  been  termed,  appears  to  be  the  conversion  of 
the  sugar  into  lactic  acid,  which  is  thereafter  oxidated  and  given 
ofi"  as  carbonic  acid  and  water. 

Liebig  has  called  attention  to  the  amount  of  oxygen  which 
enters  the  body,  and  the  very  small  quantity  that  is  retained. 
Thus,  in  the  course  of  a  year,  an  adult  male  takes  in  at  his 
lungs,  seven  hundred  and  forty-six  pounds  of  oxygen,  and  yet 
his  weight  is  not  at  all  or  only  very  slightly  increased  at  the 
end  of  that  time.  It  must,  therefore,  have  been  given  ofi"  as 
rapidly  as  it  was  received,  and  the  products  of  the  changes 
being  examined,  it  becomes  very  apparent  that  it  has  formed  a 
chemical  union  with  the  carbon  and  the  hydrogen  of  the  blood, 
which  have  then  passed  ofi"  in  the  form  of  carbonic  acid  and 
water.  When  we  except  that  portion  of  the  body  which  has 
thus  been  oxidated,  this  carbon  and  hydrogen  are  directly  fur- 
nished by  the  food,  and  in  great  part  by  its  saccharine  portion. 

But  this  is  not  the  only  purpose  subserved  by  the  saccharine 
aliments.  They  are  undoubtedly  convertible  into  fat,  and  that 
substance  is  by  no  means  an  unimportant  element  in  nutrition 
and  histogenesis.  Lehmann  has  also  shown  that  small  quanti- 
ties of  sugar  greatly  promote  the  digestion  of  the  true  nitro- 
genous aliments,  and  that  the  acids  resulting  from  the  decompo- 
sition of  this  substance,  discharge  functions  altogether  distinct 
from  respiratory  changes. 

The  oleaginous  group  of  alimentary  substances  is  also  classi- 
fied by  Liebig  under  the  head  of  respiratory  food,  and  we  shall 
presently  see,  when  we  come  to  consider  the  phenomena  of  star- 
vation, what  an  important  relation  they  sustain  to  the  function 
of  respiration.  It  would,  however,  be  an  extremely  imperfect 
view  of  the  destination  of  this  class  of  aliments,  if  we  were  to 


114  DIGESTION. 

suppose  them  entirely  used  up  in  the  respiratory  process.  We 
have  already  seen  that  fat  constitutes  the  basis  of  all  granules 
and  nuclei,  and  consequently  of  all  cell-growth ;  that  it  plays  an 
important  part  in  gastric  digestion,  and  assists  in  the  formation 
of  the  bile.  Thus,  it  is  a  very  important  element  in  nutrition, 
■while  at  the  same  time,  both  it  an(^  sugar  are  totally  incapable 
of  supporting  life  of  themselves. 

Of  the  albuminous  group  we  have  already  said  enough  under 
the  head  of  histogenetic  elements  to  show  that  it  furnishes  the 
true  nutriment  of  the  system.  Albumen,  or  one  of  its  cognate 
compounds,  is  the  substance  from  which  all  the  tissues  are  formed. 
It  is  remarkable,  however,  that  alone  it  will  not  support  life. 
When  deprived  of  the  flavoring  substance,  osmazome,  it  becomes 
so  disgusting  to  the  stomach,  that  it  is  rejected  or  not  digested, 
and  so,  while  possessing  the  necessary  elements  of  nutrition, 
fails  to  nourish. 

Dr.  Prout  has  called  attention  to  the  fact  that,  in  the  only 
instance  in  which  nature  has  supplied  an  animal  with  a  single 
article  of  food  for  its  nutrition,  she  has  compounded  it  of  sub- 
stances belonging  to  these  three  groups.  Milk  contains  casein, 
the  representative  of  the  albuminous,  sugar  and  butter  repre- 
senting respectively  the  saccharine  and  oleaginous  groups.  The 
first  of  these  substances  furnishes  the  pabulum  of  the  tissues, 
and,  as  it  enters  the  young  animal,  carries  with  it  a  large  quan- 
tity of  phosphate  of  lime,  in  the  most  soluble  form,  thus  fur- 
nishing the  little  creature  with  that  earth  which  is  to  harden  its 
growing  bones,  and  fit  them  for  the  discharge  of  their  functions. 
The  oily  matter  of  the  cream  and  the  sugar,  dissolved  in  the 
whey,  supplies  those  materials  which  are  needed  for  respiration, 
and  for  the  other  purposes  to  which  we  have  seen  they  are  ap- 
plied in  the  animal  economy. 

The  gelatinous  articles  of  food  do  not  directly  nourish  even 
the  gelatinous  tissues,  which  are  produced  by  the  metamorphosis 
of  the  protein  compounds  within  the  body.  It  has  been  sug- 
gested that  the  hydrocarbon  is  eliminated  through  the  lungs, 
and  the  azotized  portion  through  the  kidneys.  Frerichs  did  not 
find  any  leucine  or  glycine  in  the  urine  after  the  injection  of 
gelatine  into  the  veins,  but  only  an  excess  of  urea.     This  class 


FOOD.  115 

of  substances,  therefore,  seems  to  be  useful  only  in  its  calorific 
capacity,  so  that  the  nutritive  value  of  sups  must  depend  wholly 
on  the  albuminous  substances  they  hold  in  solution,  and  their 
property  of  keeping  up  the  animal  heat,  by  the  combustion  of 
the  hydrocarbons  of  their  gelatine. 

The  nutritive  properties  of  food,  so  far  at  least  as  the  forma- 
tion of  tissues  is  concerned,  must  therefore  depend  upon  the 
amount  of  albumen  ready  to  be  assimilated,  which  it  may  con- 
tain. We  say  ready  to  be  assimilated,  for  there  is  a  great  dif- 
ference in  the  facility  with  which  different  substances  enter  the 
system.  Food  may  contain  the  elements  of  nutrition  in  large 
quantity,  but,  owing  to  its  nature,  the  manner  in  which  it  has 
been  prepared,  or  the  condition  of  the  digestive  organs,  it  may 
not  be  in  a  condition  to  be  readily  taken  up.  So,  too,  the  calo- 
rific powers  of  different  articles  of  diet  cannot  be  estimated  by 
the  proportional  amount  of  hydrogen  and  carbon  they  contain, 
but  only  by  the  quantity  of  these  two  elements  uncombined  with 
oxygen.  Thus,  sugar  is  not  so  powerful  a  supporter  of  animal 
heat  as  fat,  for  the  simple  reason  that  it  has  less  of  these  ele- 
ments in  a  state  to  combine  with  oxygen  in  the  body.  Liebig 
estimates  the  calorific  power  of  fat  to  exceed  that  of  any  of  the 
other  articles  of  respiratory  food.  Thus,  if  it  would  require  100 
parts  of  fat  to  keep  up  a  given  temperature  a  given  length  of 
time,  it  would  demand  for  the  same  purpose  240  of  starch,  249 
of  cane-sugar,  263  of  grape-sugar,  and  266  of  spirits  containing 
fifty  per  cent,  of  absolute  alcohol.  We  may  get  a  still  clearer 
idea  of  this  subject,  if,  assuming  a  definite  number  for  the  calo- 
rifying  power  of  fat,  we  compare  the  other  substances  with  it. 
Thus,  then,  if  in  such  a  table,  we  represent  fat  by  100,  we 
should  have  for  starch,  41.7;  cane-sugar,  40.2;  grape-sugar, 
38;  spirits,  37.6;  and  lean  flesh  only  13.  From  these  facts,  it 
is  manifest  that  a  mixed  diet,  that  is  to  say,  a  diet  which  con- 
tains these  various  classes  of  alimentary  substances,  mingled  in 
due  proportion,  is  at  once  the  most  economical  and  the  most 
agreeable  to  man. 

"A  nation  of  hunters,"  says  Liebig,  "in  a  limited  space,  is 
utterly  incapable  of  increasing  its  numbers  beyond  a  certain 
point,  which  is  soon  attained.     The  carbon  necessary  for  respi- 


116  DIGESTION. 

ration  must  be  obtained  from  the  animals,  of  which  only  a  limited 
number  can  live  on  the  space  supposed.  These  animals  collect 
from  plants  the  constituents  of  their  organs  and  of  their  blood, 
and  yield  them  in  turn  to  the  savages,  who  live  by  the  chase 
alone.  They,  again,  receive  this  food  unaccompanied  by  those 
compounds,  destitute  of  nitrogen,  which,  during  the  life  of  the 
animals,  served  to  support  the  respiratory  process.  In  such 
men,  confined  to  an  animal  diet,  it  is  the  carbon  of  the  flesh  and 
of  the  blood  which  must  take  the  place  of  starch  and  sugar. 

"But  fifteen  pounds  of  flesh  contain  no  more  carbon  than 
four  pounds  of  starch,  and  while  the  savage,  with  one  animal 
and  an  equal  weight  of  starch,  could  maintain  life  and  health  for 
a  certain  number  of  days,  he  would  be  compelled,  if  confined  to 
flesh  alone,  in  order  to  procure  the  carbon  necessary  for  respi- 
ration during  the  same  time,  to  consume  five  such  animals. 

"It  is  easy  to  see,  from  these  considerations,  how  close  the 
connection  is  between  agriculture  and  the  multiplication  of  the 
human  species.  The  cultivation  of  our  crops  has  ultimately  no 
other  object  than  the  production  of  a  maximum  of  those  sub- 
stances which  are  adapted  for  assimilation  and  respiration,  in 
the  smallest  possible  space.  Grain  and  other  nutritious  vege- 
tables yield  us  not  only  in  starch,  sugar,  and  gum  the  carbon 
which  protects  our  organs  from  the  action  of  oxygen,  and  pro- 
duces in  the  organism  the  heat  which  is  essential  to  life,  but 
also  in  the  form  of  vegetable  fibrin,  albumen,  and  casein,  our 
blood,  from  which  the  other  parts  of  the  body  are  developed. 

"Man,  when  confined  to  animal  food,  respires  like  the  carni- 
vora,  at  the  expense  of  the  matters  produced  by  the  metamor- 
phosis of  organized  tissues,  and  just  as  the  lion,  tiger,  and 
hyena  in  the  cages  of  a  menagerie,  are  compelled  to  accelerate 
the  waste  of  the  organized  tissue  by  incessant  motion,  in  order 
to  furnish  the  matter  necessary  for  respiration,  so  the  savage, 
for  the  very  same  object,  is  forced  to  make  the  most  laborious 
exertions,  and  go  through  a  vast  amount  of  muscular  exercise. 
He  is  compelled  to  consume  force  merely  in  order  to  supply 
matter  for  respiration. 

"Cultivation  is  the  economy  of  force.  Science  teaches  us  the 
simplest  means  of  obtaining  the  greatest  efi'ect  with  the  smallest 


FOOD.  117 

expenditure  of  power,  and  with  means  to  produce  a  maximum  of 
force.  The  unprofitable  exertion  of  power,  the  waste  of  force 
in  agriculture,  in  other  branches  of  industry,  in  science,  or  in 
social  economy,  is  characteristic  of  the  savage  state,  or  of  the 
want  of  knowledge."* 

There  are  cases,  however,  in  which  exclusive  animal  food  is 
best  adapted  to  the  wants  of  man.  Thus,  the  Pamperos  of 
South  America,  who  live  in  the  saddle  and  hunt  like  tigers,  live 
exclusively  on  beef,  and  thrive  on  it.  So,  too,  the  Esquimaux, 
in  their  cold,  inhospitable  climate,  find  the  most  suitable  food  to 
be  the  oily  meat  of  the  whale  and  seal.  Again,  in  other  por- 
tions of  the  world,  an  exclusively  vegetable  diet  is  both  more 
agreeable  and  better  adapted  to  the  wants  of  the  inhabitants. 

Whether  the  food  be  obtained  from  plants  or  from  animals,  a 
due  mixture  of  the  albuminous,  oleaginous,  and  saccharine  ali- 
ments is  necessary.  When  violent  exercise  is  a  man's  common 
condition,  the  albuminous  food  ought  to  predominate  in  order  to 
supply  the  deficiency  caused  by  the  rapid  waste  of  the  tissues. 
For  the  colder  regions  of  the  earth,  excess  of  fat  is  necessary  in 
order  to  supply  the  necessary  materials  for  keeping  up  the  ani- 
mal heat  which  is  so  rapidly  reduced  by  the  low  temperature  of 
the  air.  The  saccharine  elements  should  preponderate  in  the 
diet  of  the  resident  in  the  tropics,  who  is  sure  to  sufi"er  from 
hepatitis  if  he  neglect  this  simple  precaution.  In  our  own  coun- 
try much  of  the  bilious  disorder  complained  of  proceeds  from 
the  quantity  of  highly  carbonaceous  food  which  is  eaten  during 
the  summer  time. 

Besides  these  classes  of  food,  fresh  vegetables  are  necessary 
to  health.  A  great  deficiency  or  a  total  want  of  these  is  sure  to 
engender  that  terrible  scourge  of  the  old  navies,  scurvy. 

Deficiency  of  the  albuminous  articles  of  food  is  directly  pro- 
ductive of  debility,  and  all  the  diseases  which  follow  in  its  train. 
Their  excess  leads  to  a  plethora  and  the  disturbances  which 
attend  that  state  of  the  system,  such  as  apoplexy,  active  hemor- 
rhage, inflammations,  gout,  &c.  Deficiency  of  the  oleaginous 
substances  is  thought  to  be  productive  of  tuberculous  and  scro- 

*  Familiar  Letters  on  Chemistry. 


118  DIGESTION. 

fulous  disease.  It  is  remarkable  that  Iceland  is  quite  free  from 
these  diseases,  an  exemption  to  be  attributed  only  to  the  amount 
of  oily  matters  taken  in  the  food.  The  marked  improvement  of 
tuberculous  patients  under  codliver  oil,  for  which  it  is  believed 
most  oils  can  be  substituted,  is  thought  by  Lehmann  to  be  ac- 
counted for  by  the  fact  to  which  we  have  already  repeatedly 
referred,  that  oil-globules  constitute  always  the  first  stage  of 
cell- development.  The  body,  failing  to  generate  or  separate 
fat  from  the  common  food,  appropriates  that  which  is  directly 
introduced  into  the  system,  and  thus  derives  at  least  a  tempo- 
rary benefit.  Excess  of  these  substances  has  already  been  cited 
as  a  prolific  source  of  hepatic  disease.  When  the  far inace a  are 
used  in  excess,  without  proper  admixture  of  other  matters,  rheu- 
matism  is  thought  to  be  the  method  in  which  nature  makes 
known  the  impropriety  of  this  course. 

The  amount  of  food  necessary  for  the  support  of  a  man  must, 
of  course,  vary  with  the  varying  circumstances  of  habit,  climate, 
and  individual  constitution.  The  more  the  system  is  wasted  by 
exercise,  the  more  albuminous  food  does  it  require,  and  this  had 
better  come  from  the  animal  kingdom,  the  food  from  which  seems 
to  enter  more  rapidly  into  the  system,  and  to  be  assimilated 
with  less  difficulty  than  that  from  any  other  source. 

Water  is  an  essential  portion  of  our  ingesta.  It  is  necessary 
to  give  the  blood  the  proper  amount  of  dilution,  which  is  so 
important  not  only  to  the  due  performance  of  the  function  of 
circulation,  but  also  to  that  of  absorption,  secretion,  and  nutri- 
tion. A  certain  degree  of  fulness  of  the  vessels  and  a  definite 
viscidity  of  the  blood  are  essential  conditions  of  health,  and  they 
are  physical  properties  which  depend  entirely  on  the  amount  of 
water  contained  in  the  vital  fluid. 

The  phenomena  of  starvation  illustrate  the  views  just  ad- 
vanced. Considered  from  a  physiological  point  of  view,  it  is 
the  excess  of  waste  over  reparation.  The  chemist  sees  in  it  a 
gradual  process  of  oxidation.  The  diminution  of  weight  is 
caused  by  losses  from  all  parts  of  the  system,  even  from  the 
bones;  but  those  parts  which  suffer  most  are  those  which  are 
most  prone  to  this  sort  of  disorganization.  The  fat  and 
the  blood,  according  to  Chossat's  experiments,  suffered  most. 


GASTRIC  DIGESTION.  119 

The  former  lost  93.3,  the  latter,  75 1^  of  their  weight,  the  whole 
body  losing  40g.  The  most  marked  symptom  of  starvation  is 
the  disappearance  of  the  fat,  and  this  is  not  to  be  found  either 
in  the  urine  or  the  feces.  It  has  passed  off  as  carbonic  acid 
and  water  through  the  skin  and  lungs.  When  it  has  gone,  the 
pabulum  of  the  lungs  has  been  removed,  the  temperature  of  the 
body  rapidly  falls,  the  tissues  are  now  attacked,  and  an  offen- 
sive fetor  is  exhaled,  indicative  of  the  putrefactive  processes 
which  are  going  on  within  the  body. 


CHAPTER    III. 

GASTRIC  DIGESTION. 

The  food,  such  as  we  have  described  it,  having  been  intro- 
duced into  the  mouth,  and  there  masticated,  and  thoroughly 
mixed  with  the  secretions  of  that  cavity,  the  influence  of  which 
will  be  hereafter  discussed,  is  propelled  into  the  stomach,  where 
it  undergoes  the  first  of  that  series  of  changes  which  is  to  assi- 
milate it  to  the  body  it  is  designed  to  nourish. 

The  nature  of  digestion  was  very  obscurely  understood;  or, 
more  properly  speaking,  it  was  not  understood  at  all  by  the 
older  physiologists,  who  used  to  talk  about  concoction,  and  tri- 
turation, and  a  variety  of  other  things,  and  tried  to  explain  it 
upon  any  and  every  principle  but  the  true  one.  It  is  now  very 
generally  understood  to  be  a  cliemical  process;  under  the  control, 
indeed,  of  the  vital  powers,  as  are  all  other  chemical  processes 
in  the  body. 

The  solvent  is  the  gastric  juice  secreted  by  the  cells  of  the 
mucous  membrane  of  the  stomach,  and  to  this  we  now  call 
attention. 

Various  methods  of  obtaining  pure  gastric  juice  for  experi- 
mental purposes  have  been  suggested  by  chemists.  Tiedemann 
and  Graelin  used  to  feed  dogs,  or  make  them  swallow  irritants, 
and  then  kill  them.     In  this  manner,  they  obtained  all  the  gas- 


120  DIGESTION. 

trie  juice  used  in  their  experiments.  Spallanzani  and  others 
made  the  animals  swallow  sponges  attached  to  a  string,  and  then 
withdrew  them  from  the  stomach.  The  objection  to  these  me- 
thods is  that  there  is  an  inevitable  admixture  of  saliva  with  the 
fluid  thus  obtained.  Of  late  years,  this  fluid  has  been  obtained 
from  fistulous  openings  in  the  stomach.  Dr.  Beaumont  was  the 
first  to  adopt  this  method.  He  procured  the  fluid  for  his  famous 
experiments  from  the  stomach  of  Alexis  St,  Martin,  in  whom 
such  a  fistula  had  fortunately  been  established  by  a  gunshot 
wound.  Since  then,  Blondlot,  Bernard,  Bardeleben,  and  others 
have  established  artificial  gastric  fistuloe  in  dogs,  and  drawn 
thence  the  fluid  for  their  researches. 

Bardeleben's  method  of  establishing  this  fistula,  to  which 
Lehmann  gives  the  preference  above  all  others,  is  to  make  an 
incision  two  inches  long  from  the  ensiform  process  towards  the 
umbilicus,  exactly  in  the  linea  alba ;  to  open  the  peritoneum  an 
equal  length,  to  seize  the  stomach,  draw  out  a  fold,  pass  a  needle 
through  it,  make  it  fast  to  a  peg  laid  across  the  wound,  which 
is  closed  with  sutures,  taking  care  that  the  fold  is  contained  in 
that  portion  of  the  wound  nearest  the  navel,  and  then  to  wait 
for  the  sloughing  of  the  stomach.  This  takes  place  from  the 
third  to  the  fifth  day;  the  walls  of  the  organ  adhere  to  the 
sides  of  the  wound,  and  the  fistula  is  complete.  Into  this  is 
inserted  a  small  silver  tube  about  three-fourths  of  an  inch  long, 
made  fast  by  a  couple  of  double  hooks,  and  closed  by  a  cork.  It 
is  remarkable  that  the  health  of  the  poor  animals  sufi'ers  but 
little  from  this  torture. 

Pure  gastric  juice  is  perfectly  clear  and  transparent,  almost 
colorless,  having  at  most  a  pale-yellowish  tint,  and  possessing  a 
faint,  peculiar  odor,  and  a  taste  partly  saline  and  partly  acid.  It 
contains  a  few  gastric  cells  and  nuclei,  and  some  disintegrated 
molecular  matter.  Its  reaction  is  strongly  acid.  It  is  not  ren- 
dered turbid  by  boiling  unless  its  free  acid  has  first  been  neutral- 
ized. It  very  powerfully  resists  decomposition,  and  retains  its 
digestive  powers  even  after  a  vegetable  mould  has  formed  upon  it. 

Its  specific  gravity  is  but  little  higher  than  that  of  water,  and 
it  contains  but  a  small  quantity  of  solid  matter.  In  dogs,  this 
varies  from  1  to  1.48^.     In  a  horse,  Frerichs  found  1.72^;  and 


GASTRIC  DIGESTION.  121 

from  some  human  gastric  juice  collected  by  Dr.  Beaumont,  Ber- 
zelius  obtained  1.27^  of  solid  constituents. 

There  has  been  much  controversy  regarding  the  free  acid  of 
the  gastric  juice.  Some  chemists  have  declared  that  it  is  hydro- 
chloric acid,  while  others  are  equally  positive  that  it  is  lactic, 
and  Blondlot  asserts  that  there  is  no  free  acid  at  all  in  this 
fluid,  and  attributes  the  reaction  to  the  acid  phosphate  of  lime. 
His  reasons  for  this  opinion  are  that  he  failed  to  dissolve  car- 
bonate of  lime  in  the  gastric  juice,  which  ought  not  to  have  been 
the  case  if  there  were  a  free  acid  present.  It  has  since  been 
shown,  however,  that  when  the  gastric  juice  is  sufficiently  con- 
centrated, it  will  dissolve  not  only  carbonate  but  phosphate  of 
lime,  and  also  iron  and  zinc,  hydrogen  being  evolved,  a  solution 
which  the  biphosphate  of  lime  is  totally  inadequate  to  effect. 
Dumas  goes  farther,  and  asserts  that  there  is  no  biphosphate  of 
lime  to  be  found  in  the  stomach. 

Dr.  Prout  advanced  the  opinion  that  free  hydrochloric  acid 
caused  this  strong  acid  reaction.  He  distilled  gastric  juice,  and, 
on  precipitating  the  acid  liquid  which  passed  over  with  nitrate 
of  silver,  he  obtained  the  chloride  of  that  metal.  Dunglison 
procured  the  same  acid  from  Alexis  St.  Martin's  gastric  juice. 

Many  excellent  observers,  however,  deny  the  presence  of  this 
acid,  although  there  can  be  no  doubt  that  it  does  pass  over  in 
distillation.  Bernard  and  Barreswil  account  for  this  by  suppos- 
ing that  hydrochloric  acid,  which,  they  say,  passes  over  only 
towards  the  close  of  the' distillation,  is  formed  by  the  mutual 
reaction  of  the  elements  of  the  concentrated  juice.  They  cor- 
roborate this  opinion  by  the  results  of  experiments  on  what  they 
suppose  to  be  analogous  mixtures.  Thus,  when  they  distilled  a 
solution  of  chloride  of  sodium  with  lactic  acid,  they  found  that, 
toward  the  close  of  the  process,  hydrochloric  acid  came  over. 
Lehmann  adopts  very  much  the  same  opinion,  and  states  that 
even  when  gastric  juice  is  evaporated  in  vacuo,  he  has  obtained 
as  much  as  0.125g  of  hydrochloric  acid  from  the  vapor  that 
passed  off.  This,  he  thinks,  is  also  produced  by  the  same  de- 
composition ;  and  he  finds,  by  experiment,  that  chloride  of  cal- 
cium, but  not  chloride  of  sodium,  as  Bernard  and  Barreswil 
assert,  can  be  decomposed  by  evaporating  it  with  lactic  acid  in 


122  DIGESTION. 

vacuo.  Still  farther,  in  objection  to  the  hydrochloric  acid  theory, 
it  has  been  urged  by  Bernard  and  Barreswil  that  oxalic  acid 
throws  down  lime  from  the  gastric  juice,  a  reaction  which  can- 
not take  place  in  a  solution  containing  only  the  thousandth 
part  of  hydrochloric  acid.  Farthermore,  starch,  when  boiled 
with  hydrochloric  acid,  loses  the  property  of  becoming  blue 
when  treated  with  iodine,  but  lactic  acid  does  not  affect  it. 
Starch,  it  is  asserted,  still  strikes  the  blue  tint  with  iodine, 
after  being  boiled  in  gastric  juice. 

That  lactic  acid  is  the  acidifying  principle,  Bernard,  and  Bar- 
reswil, and  Lehmann  claim  to  have  proved  both  directly  and 
indirectly.  The  first-named  chemists  have  found  with  the  gas- 
tric acid,  salts  of  lime,  baryta,  copper,  and  zinc  soluble  in  water, 
a  salt  of  lime  soluble  in  alcohol  and  precipitable  from  this  solu- 
tion by  ether,  and  a  double  salt  of  copper  and  lime  of  a  deep 
color ;  all  which  reactions  correspond  with  those  of  lactic  acid. 

Bernard  attempts  to  strengthen  this  position  by  experiments 
on  the  results  of  the  injection  of  difi"erent  fluids  into  the  blood. 
He  finds  that  a  food  digested  in  gastric  juice,  and  mixed  with  a 
very  small  quantity  of  hydrochloric  acid,  when  injected  into  the 
veins,  speedily  destroys  life.  In  experimenting  on  the  salts  of 
iron,  in  the  same  way,  he  found  that  the  lactate  was  the  only 
one  which  did  not  destroy  life.  It  is  difficult  to  see  the  bear- 
ing of  such  experiments  as  these  upon  the  question  ;  as  the  rude 
pushing  of  an  injection  into  the  veins  can  in  nowise  resemble 
the  gradual  process  of  absorption  from  the  stomach  and  intes- 
tines. Besides,  if  we  are  to  believe  Wright's  experiments,  a 
fluid,  like  the  saliva,  which  is  daily  introduced  in  large  quanti- 
ties into  the  stomach  with  perfect  impunity,  cannot  be  thrown 
into  the  veins  without  serious  and  even  fatal  mischief  ensuing. 

Lehmann  has  adopted  a  more  practical  method  of  deciding 
the  question.  He  has  separated  the  lactic  acid  and  determined 
its  quantity.  Thus,  in  evaporating  gastric  juice  to  dryness  in 
vacuo,  he  obtained  from  0.098  to  0.132  per  cent,  of  free  hydro- 
chloric acid  from  the  vapor,  and  0.320  to  0.583g  of  lactic  acid 
from  the  residue;  so  that,  if  the  acidity  had  depended  exclu- 
sively upon  this  acid,  there  must  have  been  from  0.561  to 
0.908g  of  it  in  the  gastric  juice. 


GASTRIC  DIGESTION.  123 

On  the  other  side  of  the  question,  however,  there  is  much  to 
be  said.  Liebig  denied  the  presence  of  this  acid  in  the  gastric 
juice,  and  asserted  that  its  solvent  powers  were  too  feeble  for  it 
to  be  of  any  service  if  it  were  there.  Enderlin,  on  examining 
the  stomach  of  a  recently  beheaded  criminal,  failed  to  detect  it, 
a  circumstance  to  which  Lehmann  alludes  with  a  perceptible 
sneer.  To  the  smell  of  hydrochloric  acid  in  fresh  gastric  fluid, 
alluded  to  by  Professor  Dunglison,  but  little  importance  can  be 
attached.  It  is  difficult  for  any  one  who  has  manipulated  with 
hydrochloric  acid,  to  understand  how  so  minute  a  quantity  of  it, 
mingled  with  so  much  animal  fluid,  could  be  distinguished  by  the 
most  acute  nasal  organs. 

The  most  conclusive  fact  that  has  been  adduced  on  this  side 
of  the  question,  is  the  analysis  recently  made  by  Professor  Gra- 
ham, of  London.  Dr.  Bence  Jones  having  procured  some  pure 
gastric  fluid,  submitted  it  to  that  distinguished  chemist  for  exa- 
mination. He  proceeded  by  his  method  of  "liquid  difi"usion," 
which  is  not  liable  to  the  objections  that  have  been  urged  against 
distillation,  and  obtained  free  hydrochloric  acid.  Lactic  acid 
was  also  present,  but  in  small  quantity. 

Carpenter,  in  his  Principles  of  Human  Physiology,  suggests 
that  while  lactic  acid  may  be  the  solvent  in  the  stomachs  of 
dogs  and  pigs,  the  animals  experimented  on  by  the  first-named 
chemists,  it  does  not  necessarily  follow  that  it  must  also  be  the 
free  acid  present  in  human  gastric  fluid.  Neither  Lehmann, 
Blondlot,  nor  Bernard  appear  to  have  subjected  the  contents  of 
a  man's  stomach  to  analysis,  while  it  is  upon  human  juices  that 
Prout,  Dunglison,  Enderlin,  and  Graham  have  experimented. 
This  may  account  for  the  discrepancy  existing  among  such  emi- 
nent observers.  Both  hydrochloric  and  lactic  acids  seem  to  be 
able  to  confer  on  gastric  juice  its  solvent  power,  and  to  be  capable 
of  being  substituted  for  one  another ;  so  that  lactic  acid  may 
be  the  chief  source  of  the  acidity  in  the  lower  animals,  and 
hydrochloric  acid  in  man. 

The  solid  residue  of  the  gastric  juice  contains  also  chloride  of 
sodium  in  abundance,  chlorides  of  calcium  and  magnesium  in 
smaller  quantities,  and  traces  of  proto-chloride  of  iron.  The 
latter  may  be  recognized  in  strongly  evaporated  gastric  juice  by 


124  DIGESTION. 

means  of  ferridcyanide  of  potassium,  and  the  former  may  be 
obtained  in  crystals,  moistened  -with  a  yello"wish  syrupy  mass, 
consisting  chiefly  of  lactate  of  soda. 

PJiosj^hate  of  lime  is  present  in  small  quantities  in  the  filtered 
fluid.  When  much  mucus  or  many  cells  are  found  in  it,  this  salt 
exists  in  greater  proportion.  Alkaline  sulphates  and  phosphates, 
and  ammoniacal  salts  are  not  to  be  found  in  pure  gastric  juice. 

There  are  also  organic  substances  present  in  this  fluid  Among 
these  are  osmazome,  and  a  substance  soluble  in  water,  but  pre- 
cipitated by  alcohol,  the  pepsin  or  digestive  principle.  The 
ratio  subsisting  between  the  organic  and  the  inorganic  consti- 
tuents, is  a  somewhat  variable  one.  In  the  horse,  Gmelin  found 
1.05^-  of  organic,  and  0.55^-  of  inorganic  constituents,  and  Fre- 
richs  discovered  0.98^  of  organic,  and  0.74g  of  inorganic  matters. 
In  the  gastric  juice  of  the  dog,  Frerichs  found  0.72^  of  organic, 
and  0.432  of  inorganic  constituents,  while  Lehmann  obtained 
from  0.86  to  0.99g  of  the  former,  and  from  0.38  to  0.56§  of  the 
latter. 

It  has  been  shown  that  an  artificial  gastric  juice,  which  would 
digest  food  out  of  the  body,  can  be  formed,  and  that  it  requires 
a  free  acid  and  the  mucous  coat  of  a  stomach,  or  a  substance 
extracted  from  the  latter,  to  confer  upon  it  its  full  solvent  power. 
The  absence  of  either  of  these  is  fatal  to  the  experiment. 

Pejjsin  was  first  obtained  and  examined  by  Schwann,  who 
found  that,  from  the  glandular  structure  of  the  stomach,  he 
could  separate  a  substance  capable  of  forming  a  digestive  mix- 
ture with  acids,  and  of  being  precipitated  by  corrosive  sublimate. 

Wasmann  afterwards  examined  it  with  more  care,  and  con- 
firmed Schwann's  statement  that  it  was  obtained  from  the  gas- 
tric glands.  He  carefully  detached  that  portion  of  the  mucous 
membrane  of  the  pig's  stomach,  which  contains  the  glands,  ex- 
tending from  the  greater  curvature  towards  the  cardiac  orifice, 
washed  it  carefully,  without  cutting  it  up,  and  digested  it  in  dis- 
tilled water  at  a  temperature  of  from  86°  to  95°.  This  being 
poured  off",  removed  many  foreign  matters.  He  then  washed  it 
again,  digested  it  in  about  six  ounces  of  cold  distilled  water,  and 
washed  it  frequently  till  a  putrid  odor  began  to  develop  itself. 
He  precipitated  the  transparent,  viscid  fluid,  obtained  by  filtra- 


GASTRIC  DIGESTION.  125 

tion,  with  acetate  of  lead  or  corrosive  sublimate ;  freed  it  from 
the  metal  by  means  of  sulphuretted  hydrogen ;  washed  it  well, 
and  again  precipitated  it  with  alcohol. 

Thus  obtained,  it  falls  in  white  flocks,  which  dry  to  a  yellow 
or  gray,  gummy,  slightly  compact,  hygroscopic  mass.  After  dry- 
ing, it  is  but  sparingly  soluble  in  water,  yielding  a  turbid  solution, 
which  still  possesses  the  characteristic  properties  of  this  substance, 
though  greatly  diminished.  In  the  moist  state,  however,  it  is 
readily  soluble  in  water.  Alcohol  precipitates  it  from  its  watery 
solution ;  mineral  acids  first  cloud  the  solution,  and  then,  when 
added  in  slight  excess,  clear  it  up  again.  Metallic  salts  precipitate 
it  imperfectly,  ferrocyanide  of  potassium  not  at  all,  and  heat 
does  not  coagulate  it  when  it  is  entirely  unmixed  with  albumen. 

Lehmann  objects  to  this  mode  of  Wasmann's,  that  it  never 
obtained  the  artificial  gastric  juice  pure,  but  always  mixed  up 
with  putrid  substances  and  partly  digested  particles  of  food.  He 
has,  therefore,  adopted  the  following  method,  which  is  given  in 
his  own  language. 

"  The  stomach  of  a  recently  killed  pig  having  been  properly 
cleaned,  I  detached  from  it  the  portion  of  mucous  membrane  in 
which  the  gastric  glands  chiefly  lie. 

As  this  piece  of  mucous  membrane  still  contains  a  tolerably 
thick  layer  of  submucous  areolar  tissue,  or  of  the  so-called  vas- 
cular coat,  in  which  the  gastric  glands  are  in  a  manner  imbedded, 
this  cannot  be  at  once  employed  in  the  preparation  of  the  diges- 
tive fluid,  since  then  a  quantity  of  digested  gelatinous  substance 
would  be  mixed  with  it.  This  source  of  error  cannot  be  entirely 
avoided,  since,  in  every  mode  of  treatment,  heterogeneous  elements 
of  tissue  will  be  mingled  with  the  glandular  contents.  In  order, 
however,  to  obtain  the  latter  in  as  pure  a  state  as  possible,  the 
piece  of  mucous  membrane,  after  being  an  hour  or  two  in  dis- 
tilled water,  at  the  ordinary  temperature,  must  be  gently  scraped 
with  a  blunt  knife  or  spatula;  the  pale,  grayish-red,  tenacious 
mucus  which  adheres  to  the  blade,  must  be  placed  in  distilled 
water,  and  the  mixture  must  be  kept  at  the  ordinary  temper- 
ature for  two  or  three  hours,  being  frequently  shaken  in  the 
interval ;  a  little  free  acid  must  then  be  added,  and  the  mixture 
placed  for  half  an  hour  or  an  hour  in  a  hatching  oven,  at  a 


126  DIGESTION. 

temperature  of  from  35°  to  38°.*  By  this  time,  the  fluid  will 
be  found  to  have  lost  much  of  its  viscidity ;  it  is  now  only 
slightly  turbid,  and  it  passes  readily  through  the  filter,  in  the 
form  of  a  perfectly  limpid  fluid,  with  a  scarcely  perceptible  yel- 
low tint. 

These  and  similar  artificial  mixtures  are  of  much  service,  as 
experience  has  indeed  fully  shown,  in  the  investigations  of  differ- 
ent conditions  and  phenomena  in  relation  to  digestion  ;  but  they 
are  far  less  suited  than  the  gastric  juice  discharged  from  the 
living  animal  for  experiments,  having  for  their  object  to  isolate 
as  much  as  possible  from  the  unessential  ingredients,  and  to  ren- 
der fit  for  chemical  analysis,  the  true  digestive  principle,  or  the 
group  of  .substances  which  constitute  it.  If  the  gastric  juice 
from  the  living  animal  be  always  mixed  with  a  little  saliva,  that 
fluid  interferes  far  less  with  an  accurate  analysis  than  the  albu- 
men and  the  diff"erent  peptones  in  the  artificial  digestive  fluids ; 
and  even  if  we  could  separate  the  albumen,  the  peptones  would 
still  be  associated  with  the  digestive  principle,  as,  indeed,  they 
are  even  with  the  natural  gastric  juice,  although  in  a  far  less 
degree.  Notwithstanding  the  labors  of  many  observers,  it  ap- 
pears by  no  means  impossible,  that  by  repeated  investigations  we 
may  so  limit  the  digestive  principle,  as  to  find  a  chemical  ex- 
pression for  it,  whether  we  can  exhibit  the  actual  substance  or 
not.  Frerichs,  in  his  classical  article  on  digestion,  has  hit  upon 
the  right  line  of  investigation,  upon  the  only  course  which  can 
lead  to  definite  results,  when  he  precipitated  the  natural  gastric 
juice  with  alcohol ;  unless  too  much  alcohol  be  added,  the  greater 
part  of  the  peptones,  and  also  of  the  aqueous  extractive  matter 
of  the  saliva,  remains  in  solution,  as  indeed  does  a  little  pepsin. 
The  precipitate  dissolves  pretty  freely  in  water,  from  which  it 
is  precipitated  by  corrosive  sublimate,  protochloride  of  tin,  basic 
acetate  of  lead,  and  tannic  acid,  and  in  an  imperfect  manner, 
by  neutral  acetate  of  lead  ;  it  does  not  become  turbid  on  boiling, 
exhibits  strong  digestive  properties  when  treated  with  dilute 
hydrochloric  or  with  lactic  acid,  but,  like  the  gastric  juice,  is 
deprived  of  them  by  boiling,  by  absolute  alcohol,  or  by  neutral- 

*  Centigrade  equivalent  to  from  95°  to  100.4°  of  Fahrenheit's  thermo- 
meter. 


GASTRIC  DIGESTION.  127 

ization  with  alkalies  ;  in  an  alkaline  solution  it  very  soon  be- 
comes putrid,  and  in  a  neutral  one,  it  seems  to  give  rise  to  the 
formation  of  fungi ;  but  when  rendered  acid,  it  remains  a  very 
long  time  without  suffering  decomposition,  exactly  as  natural 
gastric  juice.  Frerichs  has  proved  that  the  flocks,  precipitated 
by  alcohol,  contain  sulphur  and  nitrogen."* 

It  has  been  suggested  by  Professor  C.  Schmidt  that  the  gas- 
tric juice  is  a  true  conjugated  acid,  hydrochloric  acid  being  com- 
bined with  pepsin,  and  that  this  compound  acid  forms  soluble 
compounds  with  albumen,  gluten,  chondrin,  &c.  This  pepsin- 
hydrochloric  acid  is,  according  to  this  chemist,  decomposed  at 
212°  into  coagulated  pepsin  and  hydrochloric  acid,  and  it  is 
impossible  to  reproduce  it  after  the  separation.  When  brought 
in  contact  with  an  alkali,  pepsin  is  precipitated.  He  farther  says 
that  when  an  artificial  digestive  mixture  has  lost  its  power,  it 
regains  it  on  the  addition  of  fresh  hydrochloric  acid.  Under 
these  circumstances,  he  thinks  that  the  pepsin-hydrochloric  acid 
is  liberated  from  its  compounds,  and  thus  enabled  to  act  upon 
fresh  matter,  while  the  albumen  or  other  substance  which  was 
combined  with  it  is  taken  up  by  the  hydrochloric  acid. 

Lehmann  objects  to  this  hypothesis  that  he  has  failed  to 
detect  between  the  acid  and  the  matters  digested  any  of  the  ordi- 
nary relations  between  acid  and  base ;  and  that  these  digested 
matters  are  altogether  different  from  the  substances  originally 
introduced  into  the  stomach. 

"In  regard  to  the  solvent  power  of  pepsin  for  coagulated  albu- 
men, it  was  observed  by  M.  Wasmann,  that  a  liquid  which  con- 
tains 17-10, OOOths  of  acetate  of  pepsin  and  6  drops  of  hydro- 
chloric acid  per  ounce,  possesses  a  very  sensible  solvent  power, 
so  that  it  will  dissolve  a  thin  slice  of  coagulated  albumen  in  the 
course  of  six  or  eight  hours'  digestion.  With  12  drops  of 
hydrochloric  acid  per  ounce,  the  white  of  egg  is  dissolved  in  two 
hours.  A  liquid  which  contains  J  a  grain  of  acetate  of  pepsin, 
and  to  which  hydrochloric  acid  and  white  of  egg  are  alternately 
added,  so  long  as  the  latter  dissolves,  is  capable  of  taking  up 
210  grains  of  coagulated  white  of  egg  at  a  temperature  between 
95°  and  101°. 

*  Physiological  Chemistry,  vol.  ii.  p.  47. 


128  '  DiaESTION. 

"  It  would  appear,  from  such  experiments,  that  the  hydrochlo- 
ric acid  is  the  true  solvent,  and  that  the  action  of  the  pepsin  is 
limited  to  that  of  disposing  the  white  of  egg  to  dissolve  in  hydro- 
chloric acid.  The  acid,  when  alone,  dissolves  white  of  egg  by 
ebullition,  just  as  it  does  under  the  influence  of  pepsin ;  from 
which  it  follows  that  pepsin  replaces  the  effect  of  a  high  tempe- 
rature, which  is  not  possible  in  the  stomach.  The  same  acid, 
with  pepsin,  dissolved  blood,  fibrin,  meat,  and  cheese ;  while  the 
isolated  acid  dissolved  only  an  insignificant  quantity  at  the 
same  temperature;  but,  when  raised  to  the  boiling  point,  it  dis- 
solved nearly  as  much,  and  the  part  dissolved  appeared  to  be  of 
the  same  nature.  The  epidermis,  horn,  the  elastic  tissue  (such 
as  the  fibrous  membrane  of  arteries),  do  not  dissolve  in  a  dilute 
acid  containing  pepsin.  M.  Wasmann  remarked  that  the  pep- 
sin of  the  stomach  of  the  pig  is  entirely  destitute  of  the  power 
to  coagulate  milk,  although  the  pepsin  of  the  stomach  of  a  calf 
possesses  it  in  a  very  high  degree ;  from  which  he  is  led  to  sup- 
pose that  the  power  of  the  latter  depends  upon  a  particular 
modification  of  pepsin,  or  perhaps  upon  another  substance  ac- 
companying it,  which  ceases  to  be  formed  when  the  young  ani- 
mal is  no  longer  nourished  by  the  milk  of  its  mother."*  A 
portion  of  these  views  requires  modification,  as  we  shall  presently 
see. 

The  amount  of  gastric  juice  secreted  at  any  given  time,  and 
the  circumstances  which  influence  the  activity  of  the  glands, 
have  been  very  carefully  studied.  From  these,  it  would  appear 
that  the  quantity  actually  secreted,  amounts  to  from  60  to  80 
oz.  a  day.  This  estimate  is  purely  approximative,  calculated 
upon  the  saturating  capacity  of  gastric  juice  for  albumen,  and 
the  amount  of  that  substance  assimilated  during  24  hours. 

The  secretion  of  this  liquid  is  influenced  by  a  great  variety  of 
circumstances.  Thus,  mechanical  irritation,  within  certain  limits, 
stimulants,  and  salt,  increase  the  activity  of  the  secernent  glands, 
and  the  quantity  of  the  secretion.  Cold  at  first  diminishes  the 
secretion  of  gastric  juice,  and  afterwards  increases  it,  apparently, 
in  consequence  of  a  reaction,  analogous  to  that  which  is  familiarly 

*  Graham,  Elements  of  Chemistry. 


GASTRIC  DIGESTION.  129 

known  to  take  place  on  the  surface  after  the  application  of  cold. 
Moderate  heat  does  not  affect  it,  but  a  high  temperature  arrests 
the  secretion,  and  brings  on  an  adynamic  condition  which  is 
speedily  fatal.  Disturbances  of  the  nervous  system,  as  anxiety, 
grief,  fear,  fever,  &c.,  materially  diminish  the  secretion. 

It  was,  at  one  time,  supposed  that  the  nervous  system  con- 
trolled digestion,  by  stimulating  secretion  and  absorption ;  and 
numerous  experiments  were  made  to  prove  that  this  influence 
was  exerted  through  the  pneumogastric  nerves.  It  was  gene- 
rally believed  that  a  section  of  these  nerves  entirely  suspended 
the  secretion  of  the  gastric  juice,  so  that  the  animals,  upon 
which  the  operation  was  performed,  died  of  inanition.  Dr. 
Reid's  experiments,  however,  proved  that  this  was  altogether 
too  broad  an  assertion,  as  he  found  those  animals  that  lived  long 
enough,  recovered  gradually  the  power  of  secretion  and  absorp- 
tion. The  truth  appears  to  be  that,  while  these  functions  are 
greatly  under  the  influence  of  the  nervous  system,  they  are  by 
no  means  entirely  controlled  by  it. 

The  result  of  the  action  of  the  gastric  juice  upon  the  food 
has  been  called  chyme,  but  it  is  by  no  means  a  homogeneous  mass. 
On  the  contrary,  the  food  is  partly  dissolved,  partly  suspended 
in  a  state  of  very  minute  division. 

The  portion  held  in  solution  is  not  merely  dissolved,  but  also 
materially  modified.  The  food  is  changed,  whether  it  be  coagu- 
lated or  not.  New  substances  are  formed  out  of  the  protein 
elements  of  the  food,  more  soluble  than  those,  and  more  easy 
of  absorption.  These  have  been  cdXlQd.  peptones,  and  they  are 
formed  by  the  action  of  the  gastric  juice  without  evolution  or 
absorption  of  gas,  and  without  the  formation  of  any  secondary 
substance. 

Thus  when  albumen,  in  its  soluble  form,  is  introduced  into 
the  stomach,  or  treated  with  natural  or  artificial  gastric  juice 
out  of  the  body,  the  first  effect  is  that  which  would  be  produced 
by  any  other  acid  ;  the  liquid  is  rendered  turbid  by  a  partial 
precipitation  of  the  albumen.  After  awhile,  however,  if  a  suffi- 
cient quantity  of  the  solvent  have  been  used,  the  turbidity  dis- 
appears, and,  as  the  process  goes  on,  the  coagulable  matter  con-» 
stantly  diminishes,  till,  at  last,  the  liquid  no  longer  gives  any 
9 


130  DIGESTION. 

trace  of  albumen,  •when  tested  by  heat,  nitric  acid,  or  any  other 
reagent. 

To  this  modification  of  normal  albumen,  Mialhe,  who  first  in- 
vestigated it,  has  given  the  name  albummose.  It  is,  as  we  have 
already  said,  not  coagulated  by  heat  or  nitric  acid,  and  the  pre- 
cipitate thrown  down  by  alcohol  is  redissolved  in  water.  It  is, 
however,  precipitated  by  the  metallic  salts,  by  creosote,  and  by 
tannin.  It  now  readily  passes  through  the  animal  membranes, 
while  albumen  refuses  to  permeate  them. 

Fibrin  undergoes  a  similar  change,  being  converted  into 
fibi'in-pejjtones. 

Casein,  when  introduced  into  the  stomach  in  its  soluble  form, 
is  coagulated.  It  requires  a  longer  time  to  be  dissolved  in  the 
gastric  juice  than  most  other  substances  belonging  to  the  class 
of  protein  compounds,  and  it  appears  that  its  digestibility  is  in 
an  inverse  ratio  with  the  firmness  of  its  coagulation.  Thus, 
according  to  Elsasser,  the  casein  of  woman's  milk,  which  only 
coagulates  into  a  sort  of  jelly,  is  more  easily  digested  than  the 
hard,  curdy  casein  of  cow's  milk. 

The  remaining  members  of  the  albuminous  group  behave  with 
the  gastric  juice  like  albumen. 

Gluten  and  the  members  of  the  gelatinous  group  are  con- 
verted into  substances  which  closely  resemble  the  peptones  just 
described,  in  their  physical,  and  in  many  of  their  chemical  pro- 
perties. The  degree  of  their  digestibility,  however,  depends 
very  much  upon  their  physical  properties,  areolar  tissue  being 
less  digestible  than  gelatine,  and  tendon  and  cartilage  being 
hardly  dissolved  at  all,  but  passing  away  usually  with  the  ex- 
crements. 

All  the  peptones,  in  the  solid  state,  are  nearly  tasteless  and 
inodorous,  of  a  pale  yellow  color,  readily  soluble  in  water, 
slightly  in  spirits,  not  at  all  in  absolute  alcohol.  They  are  not 
precipitated  by  boiling,  but  only  by  tannic  acid,  and  corrosive 
sublimate,  and  by  acetate  of  lead  if  ammonia  have  been  pre- 
viously added.  They  combine  readily  with  bases,  whether  alka- 
line or  earthy. 

Lehmann  has  never  succeeded  in  obtaining  them  perfectly 
free  from  mineral  substances.     The  proportion  of  sulphur,  ac- 


JI 


GASTRIC  DIGESTION.  131 

cording  to  him,  is  the  same  as  in  the  substances  from  which  they 
have  been  derived,  and  that  too,  in  the  same  form.  He  can, 
indeed,  detect  no  quantitative  difference  between  these  products 
and  their  originals  in  the  food,  and  compares  the  change  to  the 
metamorphosis  of  starch  into  sugar,  or  of  cholic  into  choloidic 
acid. 

Digestion,  or  the  digestive  power  of  the  gastric  juice,  is  sus- 
pended by  boiling,  by  saturating  the  free  acid  with  an  alkali  or 
even  with  phosphate  of  lime,  by  sulphurous,  arsenious,  and  tan- 
nic acids,  by  alum,  and  by  most  metallic  salts.  It  is  impeded 
by  the  addition  of  alkaline  salts  or  by  saturating  the  fluid  with 
peptones  or  other  organic  substances.  Water  will  partially 
restore  to  a  fluid  thus  saturated  its  digestive  power,  and  so  will 
a  free  acid  repeatedly  added,  provided  it  be  suitably  diluted  with 
water,  and  be  not  in  excess.  Hydrochloric  and  lactic  acid  can 
alone  constitute  with  pepsin  an  active  digestive  fluid.  Fats, 
according  to  Lehmann,  when  added  in  certain  quantities  to  the 
gastric  juice,  promote  the  conversion  of  the  protein  compounds 
into  peptones. 

Gastric  juice  exerts  no  influence  whatever  over  non-nitrogen- 
ous articles  of  food.  It  will  not,  when  rendered  alkaline,  alter 
starch  into  sugar,  as  Bernard  supposed. 

Of  the  abnormal  constituents  of  gastric  juice,  little  is  known. 
In  gastric  catarrh,  the  common  mucus  of  the  stomach  accumu- 
lates, and  undergoes  partial  decomposition;  generating,  when 
mixed  with  saccharine  and  amylaceous  food,  acetic,  butyric,  and 
lactic  acids.  The  formation  of  the  last  two  are  especially  pro- 
moted by  the  presence  of  fat,  giving  rise  to  heartburn,  &c. 

"  The  contents  of  the  stomach,  in  jpost-mortem  examinations, 
and  sometimes  also  the  matters  which  are  vomited  in  cases  of 
gastric  catarrh,  are  perfectly  neutral  or  even  alkaline  on  their 
outer  surface,  which  is  turned  towards  the  walls  of  the  stomach, 
•while  the  inner  parts  often  exhibit  a  very  strong  acid  reaction. 
This  phenomenon,  wonderful  as  it  appears  at  first  sight,  is  ob- 
viously dependent  on  the  circumstance  that  there  must  simulta- 
neously have  been  a  deficient  secretion  of  gastric  juice,  and 
such  slight  movements  of  the  stomach  as  not  to  have  sufiiciently 
mixed  the  contents  with  one  another;  and  hence,  either  that 


132  DIGESTION. 

the  inner  portions  have  undergone  one  of  the  above-mentioned 
acid  fermentations,  or  that  they  have  retained  the  acid  reaction 
peculiar  to  the  food."* 

After  extirpation  of  the  kidneys,  urea  is  secreted  by  the  gas- 
tric glands.  Many  authors  assert  that  this  substance  has  been 
formed  in  the  stomach  during  Bright's  disease.  Lehmann  has 
hitherto  failed  to  detect  it,  though  he  has  always  found  carbon- 
ate of  ammonia.  The  only  instances  in  which  he  has  detected 
urea  in  vomited  matters  have  occurred  in  hysterical  girls  who 
had  been  drinkiner  their  own  urine. 


CHAPTER    IV. 

INTESTINAL  DIGESTION. 

Digestion,  as  we  have  already  seen,  is  not  completed  in  the 
stomach.  The  farinaceous  food  is,  in  great  part,  untouched. 
The  cane-sugar  is  unchanged,  and  the  alteration  of  the  fatty 
matters  is  scarcely  perceptible.  The  pultaceous  chyme,  which 
passes  out  of  the  pylorus,  is,  as  we  have  already  said,  composed 
of  a  solution  of  the  peptones,  holding  the  undigested  matters  in 
suspension.  Much  more  remains  to  be  accomplished  before 
digestion  can  be  considered  as  completed.  The  farther  changes 
in  the  food  occur  in  the  intestinal  canal,  and  can  only  be  under- 
stood by  studying  the  secretions  that  are  discharged  into  that 
tube,  and  its  contents  after  the  various  metamorphoses  have 
been  effected. 

The  principal  secretions  which  will  demand  our  attention  are 
the  bile,  the  pancreatic  fluid,  and  the  succus  entericus,  or  intes- 
tinal juice,  all  of  which  exert  an  influence  over  digestion. 

BILE. 

Bile,  when  taken  from  the  gall-bladder,  usually  occurs  as  a 
*  Lelimann,  op.  cit.  ii.  51. 


INTESTINAL  DIGESTION.  133 

mucous,  transparent  fluid,  capable  of  being  dra"\yn  out  in  threads, 
of  a  green  or  brown  color,  a  bitter  but  not  astringent  taste,  with 
sometimes  a  sweetish  after-taste,  and  an  odor,  which,  on  warm- 
ing the  fluid,  often  resembles  musk.  It  does  not  difi"u3e  itself 
readily  through  water  unless  the  mixture  be  stirred ;  is  usually 
alkaline,  often  neutral,  and  rarely  acid.  Mixed  with  mucus,  it 
putrefies  readily,  but  when  that  substance  is  removed,  putrefac- 
tion is  diflScult  to  induce.     Its  specific  gravity  is  about  1.02. 

It  has  been  procured  for  purposes  of  analysis  and  for  physio- 
logical experiments,  by  establishing  fistulas,  leading  either  into 
the  ductus  communis  choledochus  or  into  the  gall-bladder.  In 
either  case,  peritonitis  is  likely  to  set  in  and  destroy  the  subject 
of  the  experiment. 

The  most  widely  difierent  views  have  ever  been  held  by 
physiologists  and  chemists,  not  only  in  regard  to  the  functions 
of  the  liver,  but  also  in  reference  to  the  nature  of  the  bile  itself. 
In  our  account  of  it,  we  shall  follow  Lehmann,  who  has  himself 
been  guided  by  Liebig. 

All  bile  contains  two  essential  ingredients,  a  resinous  and  a 
coloring  matter.  The  resinous  constituent  is  glycine  or  taurine 
conjugated  with  an  acid.  The  coloring  principle  has  already 
been  described;  it  is  combined  with  an  alkali.  Besides  these, 
we  always  find  in  bile  cholesterin,  fats,  and  fatt2/  acids  com- 
bined with  alkalies,  as  well  as  the  various  mineral  salts,  chloride 
of  sodium,  phosphate  and  carbonate  of  soda,  phosphates  of  lime 
and  magnesia,  iron,  manganese,  but  no  sulphates  of  the  alkalies. 
It  is  remarkable  that  the  bile  of  salt-water  fishes  contains  almost 
exclusively  potash  salts,  while  that  of  the  herbivorous  mammalia 
contains  as  great  a  proportion  of  soda  salts.  The  presence  of 
copper  in  this  fluid  has  been  already  stated.  Finally,  mucus 
and  epithelium  are  always  mixed  with  it.  The  cells  of  the  lat- 
ter are  the  only  morphological  elements  to  be  found  in  healthy 
bile. 

Bile  is  so  variable  a  fluid  in  different  animals  that  we  shall 
pay  no  attention  to  the  quantitative  examination  of  any  but 
human  bile. 

According  to  Frerichs,  normal  human  bile  contains  about  14^ 
or  a  little  more  of  solid  constituents.     Gorup  Besanez  found 


134  DIGESTION. 

9.13^  of  solid  constituents  in  the  bile  of  an  old  man,  and  17.19g 
in  that  of  a  child  of  twelve  years  of  age;  but  it  requires  farther 
investigation  to  determine  whether  the  bile  of  the  aged  is  always 
more  dilute  than  that  of  the  young.  The  organic  constituents 
of  human  bile  amount  to  about  87§  of  the  whole  solid  residue. 
Of  these,  the  alkaline  taurocholates  and  glycocholates  constitute 
by  far  the  greater  proportion,  amounting  to  at  least  75 g  of  the 
entire  solid  constituents  of  this  fluid. 

Bensch  and  Strecker  have  shown  that  the  bile  of  most  animals 
contains  a  preponderating  quantity  of  taurocholate  of  soda.  As 
this  salt  (NaO.C52Hj4NOj3S)  contains  six  per  cent,  of  sulphur, 
the  taurocholic  acid,  present  in  any  given  specimen  of  bile,  is 
easily  calculated  from  the  amount  of  sulphur  present  in  that 
portion  of  it  which  is  only  soluble  in  alcohol. 

Berzelius  obtained  12. 7§^  of  ash  from  ox-bile,  the  only  variety 
of  bile  which  has  as  yet  been  carefully  examined  for  the  deter- 
mination of  the  inorganic  constituents.  According  to  \Yeiden- 
busch,  it  contains  27. 7§  of  chloride  of  sodium,  16§  of  tribasic 
phosphate  of  soda,  3.025§  of  basic  phosphate  of  lime,  1.52§  of 
basic  phosphate  of  magnesia,  0.235-  of  peroxide  of  iron,  and 
0.36^  of  silver. 

According  to  Lehmann,  bile  contains  preformed  alkaline  car- 
bonates, the  presence  of  which  he  demonstrates  by  exhausting 
in  the  receiver  of  an  air-pump  till  it  appears  to  boil,  perfectly 
fresh  bile,  from  which  the  mucus  has  been  removed.  After  this, 
he  saturates  it  with  acetic  acid,  and  by  again  surrounding  it 
with  a  vacuum,  very  large  quantities  of  carbonic  acid  are  evolved. 
In  100  parts  of  fresh  ox-bile  he  found,  at  one  time,  0.0846,  and 
at  another,  0.1124  parts  of  simple  carbonate  of  soda. 

In  normal  human  bile,  Frerichs  found  from  0.20  to  0.25^  of 
chloride  of  sodium,  and  an  equal  quantity  of  phosphate  of  soda. 

There  is  a  difiiculty  in  determining  the  quantity  of  mucus  in 
bile  on  account  of  the  epithelium  which  is  mingled  with  it. 
When  this  source  of  fallacy  was  removed  as  much  as  possible, 
Lehmann  found  0.158  of  mucus  in  human  bile. 

The  abnormal  variations  of  bile  are  numerous,  but  little 
understood.  Albumen  has  been  found  in  it,  in  fatty  liver,  in 
Bright's  disease,  and  in  the  embryo.      Urea  occurs  in  it  after 


INTESTINAL  DIGESTION.  135 

the  extirpation  of  the  kidneys,  as  well  as  in  Bright's  disease, 
and  in  cholera.  It  has  also  been  found  in  the  alcoholic  extract 
of  the  bile  of  a  man  who  died  with  fatty  degeneration  of  the 
kidneys.  Lehmann  has  found  sulphide  of  ammonium  in  the 
bile  of  a  child  dying  suddenly. 

The  solid  constituents  of  the  bile  are  diminished  after  severe 
inflammatory  aifections  and  dropsies,  in  typhus,  diabetes,  and 
often  in  tuberculosis.  They  are  usually  increased  in  those  dis- 
eases in  which  the  motion  of  the  blood  in  the  great  vessels  is 
diminished,  as  in  disease  of  the  heart,  when  the  blood  accumu- 
lates in  the  vena  cava  and  the  hepatic  veins.  In  cholera,  the 
same  increase  of  density  has  been  noticed. 

Biliary  calculi  usually  contain  a  preponderating  proportion 
of  cholesterin,  many  of  them  being  formed  exclusively  of  this 
substance,  and  a  combination  of  the  bile-pigment  with  lime. 
Rarely,  carbonate  and  phosphate  of  lime  are  the  principal  in- 
gredients. Uric  acid  is  an  occasional  constituent  of  gall-stones. 
According  to  Bramsen,  the  formation  of  the  majority  of  these 
concretions  depends  upon  the  separation  of  the  combination  of 
"bile-pigment  and  lime  already  alluded  to,  which  forms  the  nu- 
cleus of  the  calculus.  The  ratio  of  ash  varies  from  8.5  to  54.7^. 
Carbonate  of  lime,  oxalate  of  lime,  and  the  earthy  phosphates 
have  been  found  in  the  ash. 

Mucus  and  epithelium  generally  yield  the  points  around  which 
the  deposition  of  solid  matter  takes  place.  Pigment-lime  is  also 
found  in  the  centre,  whence  it  would  appear  probable  that  it 
takes  a  part  in  the  formation  of  the  calculus.  It  is  unknown 
whether  the  bile  around  this  crystallization  point  be  healthy  or 
not.  At  any  rate,  cholesterin  and  the  pigment-lime  are  sepa- 
rated from  their  solution,  and  collected  around  this  nucleus.  An 
interesting  question  is  suggested  by  these  facts  :  what  holds  the 
cholesterin  and  the  pigment-lime  in  solution  in  normal  bile  ? 
This  is  answered  by  a  very  simple  experiment.  If  the  insoluble 
residue  of  a  brown  gall-stone  be  digested  with  taurocholic  acid, 
or  acid  taurocholate  of  soda,  it  is  entirely  dissolved,  with  the 
exception  of  a  few  grayish-white  flocculi,  and  the  previously 
colorless  fluid  assumes  the  tint  of  fresh  bile. 

The  quantity  of  bile  secreted  in  a  given  time  has  been  vari- 


136  DIGESTION. 

ously  estimated  by  different  observers.  In  the  human  subject, 
some  have  rated  it  at  one  ounce,  others  at  twenty-four  ounces  in 
the  twenty-four  hours.  Blondlot,  from  his  observations  on  the 
flow  of  bile  from  fistulous  openings  established  in  dogs,  estimated 
the  secretion  in  one  of  these  animals  at  from  40  to  50  grammes 
in  the  twenty-four  hours,  and  calculated  the  amount  secreted  by 
man  during  the  same  time,  at  200  grammes,  or  between  6  and  7 
ounces.  Bidder  and  Schmidt,  who  experimented  on  cats,  state 
that  when  digestion  is  most  active,  that  is,  when  biliary  secre- 
tion is  most  abundant,  one  of  these  animals  secretes  0.765  of  a 
gramme,  or  11.907  grains,  corresponding  to  0.050  or  .772  of  a 
grain  in  an  hour  ;  while,  after  ten  days'  fasting,  it  secretes, 
during  the  same  time,  only  0.094  of  a  gramme,  or  1.249  grains, 
containing  0.0076  of  a  gramme,  or  0.1173  of  a  grain. 

The  secretion  is  continuous,  but  augmented  or  diminished  in 
accordance  with  the  state  of  the  digestion.  It  attains  its  maxi- 
mum, according  to  the  above-named  observers,  ten  or  twelve 
hours  after  a  full  meal,  and  then  diminishes  till  twenty-four 
hours  have  elapsed.  In  prolonged  starvation,  its  quantity  gradu- 
ally and  progressively  diminishes. 

The  same  observers  instituted  a  series  of  experiments  on 
numerous  animals,  to  ascertain  the  quantitative  relation  of  bile 
to  the  other  excretions.  They  first  directed  their  attention  to 
the  excretion  of  carbon,  and  found  that,  "  only  from  1-lOth  to 
l-40th  of  the  carbon  separated  by  the  lungs  is  secreted  in  an 
equal  time  by  the  liver  in  the  form  of  bile,  so  that  at  least 
8-9ths  or  9-lOths  of  the  burned  and  expired  combustible  mate- 
rials do  not  pass  through  the  intermediate  stage  of  bile,  but  re- 
main in  the  circulating  blood,  where  they  become  thoroughly 
oxidized." 

The  question  of  the  origin  of  the  bile,  as  Lehmann  very  pro- 
perly observes,  must  necessarily  precede  all  speculations  on  its 
physiological  uses,  because  all  theories  of  the  use  of  this  liquid 
necessarily  either  include  or  look  back  to  its  origin  and  mode  of 
formation. 

In  investigating  this  subject,  we  are  met,  in  limine,  by  the 
question :     Does  the  bile  exist  already  formed  in  the  blood,  or  is 


INTESTINAL  DIGESTION.  137 

it  formed  from  heterogeneous  materials  in  the  liver  ?  Upon  the 
answer  given  to  this  question,  depends  all  our  future  opinions. 

Lehmann,  who,  as  we  have  already  said,  adopts  the  first- 
named  opinion,  argues  from  anatomical  considerations  as  well  as 
from  chemical  results.  The  direct  intervention  of  so  large  a 
layer  of  cells,  actively  engaged  in  absorbing  materials  from  the 
blood,  between  the  smallest  bloodvessels  and  the  radicles  of  the 
bile-ducts,  manifestly  intimates  that  something  more  than  mere 
transudation  takes  place  in  this  organ ;  that  a  true  metamorphosis 
of  absorbed  substances  is  effected  within  these  cells.  So,  when 
Miiller,  and,  after  him,  Kunde,  extirpated  the  livers  of  frogs, 
the  blood  of  the  animals,  when  examined  after  several  days  had 
elapsed,  gave  no  indications  whatever  of  the  presence  of  bile, 
which  it  ought  to  have  done,  did  the  liver  merely  separate  from 
the  mass  of  the  circulating  fluid  a  substance  which  already  ex- 
isted in  it.  When  the  kidneys  are  extirpated,  urea  is  always 
found  in  the  blood. 

Lehmann  farther  calls  attention  to  the  peculiarity  of  the 
hepatic  circulation.  Every  tyro  in  physiology  knows  that  this 
organ  separates  its  secretion  from  the  blood  of  a  vein,  which  is 
made  up  of  radicles  coming  from  all  the  chylopoietic  viscera,  the 
liver  itself  not  excepted.  This  blood  must  necessarily  be  charged 
with  nutrient  materials,  as  well  as  with  much  excrementitious 
matter  resulting  from  the  disintegration  of  the  organs  whence  it 
is  derived.  Provision  is  also  made  for  detaining  it  some  time  in 
the  liver,  by  spreading  it  out  in  a  double  set  of  capillaries,  and 
thus  not  only  increasing  friction,  but  greatly  enlarging  the 
venous  area  of  the  abdomen  in  comparison  with  the  space  occu- 
pied by  arterial  blood.  This  remarkable  anatomical  structure 
is  easily  accounted  for  on  the  hypothesis  of  an  active  formation, 
and  not  the  mere  passive  transudation  of  a  secretion  in  the  cells 
of  the  liver.  In  the  former  case,  the  time  which  is  actually  con- 
sumed in  consequence  of  these  arrangements,  would  be  neces- 
sary to  the  perfect  function  of  the  cells. 

It  has  been  argued  against  this  view  that,  during  jaundice, 
bile  is  found  in  the  blood,  just  as  urea  is  discovered  in  the  blood 
when  the  secretion  of  the  kidneys  is  arrested.  The  phenomena 
of  jaundice,  however,  have  been  too  imperfectly  studied,  and  its 


138  DIGESTION. 

causation  is  altogether  too  obscure  to  enable  us  to  form  from  it 
any  opinion  of  the  method  in  which  the  liver  acts.  It  is  re- 
markable, also,  that  this  aiFection  rarely  or  never  occurs  in 
parenchymatous  affections  of  the  liver,  in  which  the  secreting 
power  of  that  viscus  must  be  annulled,  whereas,  it  is  very  com- 
mon in  obstructions  of  the  biliary  ducts,  and  even  in  disorder  of 
the  duodenum.  Such  facts  as  these  would  seem  to  show  that 
the  bile  is  first  formed,  and  then  reabsorbed  into  the  circulation. 

The  chemistry  of  the  blood  of  the  portal  vein,  as  compared 
with  that  of  the  hepatic  veins,  will  also  throw  light  on  this  sub- 
ject, although  the  present  resources  of  organic  analysis  are  too 
incomplete  to  solve  many  of  the  questions  which  arise  during 
the  progress  of  such  an  investigation.  The  intermixture  of 
hepatic  blood  cannot  be  of  much  importance  when  we  consider 
the  small  size  of  the  artery  as  compared  with  the  portal  vein. 

When  the  blood  of  the  portal  vein  is  examined,  it  is  found 
that  none  of  the  most  important  constituents  of  the  bile  can  be 
detected  in  it.  It  was  at  one  time  thought  that  Pettenkofer's 
test  revealed  the  presence  of  the  resinous  acids,  but  when  the 
source  of  the  fallacy  in  olein  and  oleic  acid,  which  has  already 
been  noticed,  was  removed,  no  such  reaction  took  place.  There 
is,  therefore,  no  biliary  matter  in  the  blood  of  the  portal  vein, 
but  it  contains  a  remarkable  quantity  of  oleic  acid. 

Lehmann's  hypothesis  that  cholic  acid  is  a  conjugated  acid, 
composed  of  oleic  acid  and  a  carbo-hydrate,  has  already  been 
mentioned.  This  hypothesis  derives  support  from  the  fact  of 
the  great  quantity  of  olein  contained  in  the  portal  vein,  and  the 
very  small  proportion  of  it  which  is  to  be  found  in  the  hepatic 
vein.  The  fat  contained  in  the  blood  of  these  latter  vessels  is 
more  consistent,  and  contains  a  larger  proportion  of  margarin. 
There  is  also  more  fat  of  all  kinds  in  portal  than  in  hepatic 
blood,  the  former  containing  3.2255,  while  the  latter  has  only 
1.88.5g. 

The  similarity  of  the  reactions  of  oleic  and  cholic  acids  is 
another  circumstance  which  gives  probability  to  this  view  of 
Lehmann's.  Kunde  found  that  the  fat  of  frogs,  and  indeed  of 
all  other  fats  which  contain  olein,  whether  they  be  derived  from 
the  animal  or  the  vegetable  kingdom,  give  an  intense  violet- 


INTESTINAL  DIGESTION.  139 

color  with  sulphuric  acid  and  sugar,  and  that  this  reaction  does 
not  occur  with  any  fats  free  from  olein.  This  reaction  diifers 
from  that  of  cholic  acid,  only  in  taking  place  more  slowly  and  in 
requiring  the  presence  of  atmospheric  air.  There  are,  indeed, 
other  substances  which  may  give  this  reaction,  but  ordinary 
caution  can  avoid  all  error  from  these. 

When  the  hepatic  venous  blood  is  examined,  this  test  is  only 
found  to  give  a  reaction  with  the  ethereal  solution.  It  has 
no  effect  whatever  upon  those  matters  soluble  only  in  alcohol. 
These  two  parts  furnish  sufficient  proof  that  there  is  no  biliary 
matter  whatever  in  hepatic  blood. 

The  fact  that  less  bile  is  secreted  by  fat  than  by  lean  animals 
proves  nothing  against  this  theory;  for,  as  Lehmann  observes,  it 
is  the  very  disposition  to  the  deposition  of  fat  which  prevents 
them  from  using  their  oleaginous  matters  to  form  bile.  They 
are  fat  because  they  do  not  form  much  bile ;  they  are  not  defi- 
cient in  bile  because  they  are  fat.  Pathological  observations 
confirm  this  view ;  for  in  cases  of  fatty  liver,  in  which  the  hepa- 
tic cells  are  often  dilated  to  twice  their  normal  size  with  the 
excess  of  fat,  the  quantity  of  bile  secreted  is  very  much  below 
the  standard  of  health. 

The  occurrence  of  sugar  in  the  liver  has  already  been  men- 
tioned. Sugar  is  always  conveyed  to  the  liver,  by  the  portal 
vein,  during  the  digestion  of  vegetable  food.  This  substance  is 
always  contained  in  the  portal  vein  and  its  formative  branches, 
and  is  rarely  found  in  the  chyle.  Frerichs  thinks  that  the  sugar 
is  contained  in  the  parenchyma  of  the  liver.  By  the  loss  of  six 
atoms  of  water,  the  carbo-hydrogen  adjunct  of  Lehmann  (Cj2 
HgOg)  would  be  formed  from  the  sugar,  and  thus  cholic  acid 
might  be  generated. 

It  appears  from  numerous  observations  that  the  fats  and  sugar 
are  in  an  inverse  ratio  to  one  another  in  the  hepatic  and  portal 
veins.  Fat,  as  we  have  already  said,  predominates  in  the  por- 
tal vein,  sugar  in  the  hepatic.  Reasoning  on  this  fact,  we  might 
conclude  that  the  fat,  during  the  progress  of  metamorphosis  in 
the  liver,  had  been  converted  into  cholic  acid  and  sugar.  It 
has  already  been  shown  that,  under  certain  circumstances,  sugar 
might  result  from  the  changes  of  the  protein  compounds.     Far- 


140  '  DIGESTION. 

thermore,  the  extractive  matters  may  also  furnish  a  portion  of 
this  liver-sugar. 

Another  interesting  inquiry  is  whether  the  nitrogenous  ad- 
juncts of  cholic  acid,  glycine  and  taurine,  with  which  it  forms 
glycocholic  and  taurocholic  acids,  exist  preformed  in  the  blood. 
The  first  substance  has  never  yet  been  detected  in  the  blood  of 
the  portal  vein.  Neither  can  taurine  be  discovered  in  portal 
blood,  but  it  is  settled  that  this  blood  contains  more  sulphur 
than  that  of  the  hepatic  vein.  On  investigating  the  source  of 
this  sulphur,  Lehmann  found  in  portal  blood  a  spirit-extract- 
ive very  rich  in  sulphur.  From  this  the  taurine  may  in  part 
be  formed.  The  fibrin  also,  being  greatly  diminished  in  its 
passage  through  the  liver,  may  furnish  a  portion  of  these  nitro- 
genous adjuncts.  The  albumen  is  also  diminished,  and  if  it  be 
supposed  to  enter  into  the  formation  of  the  new  hepatic  blood- 
cells,  the  walls  of  which  contain  no  sulphur,  another  probable 
source  of  the  sulphur  of  taurine  is  pointed  out. 

The  pigment  also  is  not  to  be  found  in  portal  blood;  and,  as 
has  been  already  suggested,  appears  to  be  formed  in  the  liver 
from  haematin.  "It  appears  no  mere  image  of  the  fancy,  to 
regard  the  speckled,  distorted,  irregular  blood-corpuscles  in  the 
portal  blood  of  fasting  animals  as  cells  that  are  growing  old ;  for, 
at  all  events,  we  find  that  the  blood-cells  leaving  the  liver  by 
the  hepatic  veins,  exhibit  precisely  those  characters  which  we 
ascribe  to  young  blood-cells  ;  hence,  the  cells  of  the  portal  blood 
do  not  undergo  rejuvenescence  in  the  liver,  but  suflfer  disintegra- 
tion in  that  gland,  and  their  remains  are  in  part  (the  iron,  for 
instance)  applied  to  the  formation  of  new  blood-corpuscles,  and 
in  part  converted  into  excreted  matters ;  hence,  it  is  very  con- 
ceivable that  the  hgematin  loses  its  iron,  and  becomes  converted 
into  cholepyrrhin,  which  is  mixed  in  the  biliary  canals  with  the 
other  constituents  of  the  bile."* 

The  cliolesterm  is  a  result  of  the  general  metamorphosis  of 
tissue,  and  is  found  in  the  blood  of  the  portal  vein.  The  liver, 
therefore,  can  do  no  more  than  simply  separate  it  from  the 
blood. 

*  Lehmann,  op,  cit.  ii.  96. 


INTESTINAL  DIGESTION.  141 

"The  following  may  be  regarded  as  a  brief  abstract  of  the 
above  view  regarding  the  origin  of  bile :  While  the  non-nitrogen- 
ous and  nitrogenous  matters  conveyed  by  the  portal  vein — most 
of  which,  even  when  in  the  blood,  bear  the  character  of  sub- 
stances in  the  process  of  metamorphosis — are  applied  to  the 
formation  of  the  biliary  constituents,  substances  also  pass  into 
the  bile  which  must  be  regarded  as  the  residue  or  secondary 
products  of  the  process  which  gives  rise  to  the  formation  or 
rejuvenescence  of  blood-cells  in  the  liver ;  in  the  latter  class,  we 
must  especially  place  the  fats  and  certain  of  the  mineral  con- 
stituents, while  the  nitrogenous  substances,  fibrin  and  hsematin, 
are  the  most  important  members  of  the  former.  Hence,  we  do 
not  regard  the  bile  as  the  product  of  the  metamorphosis  of  any 
single  morphological  or  chemical  constituent  of  the  animal  body 
(neither  of  the  fat-cells  nor  of  the  albuminates);  but  we  believe 
that  several  substances,  chemically  and  morphologically  distinct 
from  one  another,  undergo  alterations  in  the  liver,  and  that  their 
individual  products  unite  in  the  nascent  state,  and  thus  form  the 
compounds  and  admixture  of  substances  which  we  find  in  the 
bile."* 

As  the  bile  descends  in  the  intestines,  it  undergoes  various 
metamorphoses,  hereafter  to  be  described,  the  results  of  which 
become  gradually  less  and  less,  rendering  it  probable  that  its 
resinous  portions  are,  as  Liebig  supposed,  resorbed  into  the 
vascular  system. 

The  long  mooted  question  of  the  excrementitious  character  of 
the  bile,  can  hardly  be  regarded  as  definitely  settled.  In  the 
foetus,  the  liver  seems  to  be  a  depuratory  organ ;  but,  in  the 
adult,  if  we  are  to  allow  the  careful  observations  of  Bidder  and 
Schmidt  to  be  conclusive,  it  would  appear  to  have  very  little 
influence  in  this  way.  Besides  this,  there  appears  to  be  no 
vicarious  action  of  the  liver  when  the  function  of  the  lungs  is 
impaired. 

The  influence  of  bile  upon  digestion  has  been  by  no  means 
satisfactorily  ascertained.  The  facts  in  reference  to  it  are 
scattered,  and  have  not  yet  been  harmonized  into  an  unobjection- 

*  Lehmann,  op.  cit.  ii.  100. 


142  DIGESTION.      " 

able  theory.  The  alkali  of  the  bile  does  really  unite  with  the 
strong  acids  of  the  chyme,  in  consequence  of  which  the  resinous 
acids  of  the  bile  are  set  free  in  the  intestines,  and  gradually 
undergo  their  metamorphoses.  Its  digestive  influence  over  fat  and 
sugar,  formerly  asserted,  has  never  been  proved,  and  is  generally 
denied,  or  limited  to  the  power  of  finely  comminuting  the  fat. 
Bernard  has  shown  that  it  arrests  fermentation,  and  others  have 
observed  that  the  contents  of  the  intestines  become  completely 
putrid  when  they  are  removed  from  the  influence  of  this  secre- 
tion. Liebig  has  proved  that  its  contents,  especially  the  cholic 
acid,  undergoes  a  gradual  resorption  in  the  intestines,  and,  pass- 
ing into  the  blood,  are  oxidized  in  order  to  keep  up  the  animal 
heat. 

Lehmann  regards  bile  as  an  incidental  product  of  the  action 
of  the  liver,  the  chief  function  of  which  he  believes  to  be  the 
formation,  or  at  least  the  rejuvenescence  of  the  blood-particles. 

PANCREATIC  JUICE. 

This  is  a  colorless,  clear,  slightly  tenacious,  tasteless,  and  in- 
odorous fluid,  with  an  alkaline  reaction.  Its  specific  gravity  is 
1.008  to  1.009.  Its  coagulum,  formed  on  the  application  of 
heat,  is  inconsiderable,  and  acids  and  alkalies  only  render  it 
slightly  turbid.  Bernard's  description  of  the  pancreatic  secre- 
tion diS"ers  from  the  above  account  given  by  Frericlis  and  Leh- 
mann. According  to  him,  it  is  viscid  and  tenacious,  and  when 
heat  is  applied,  the  whole  mass  solidifies. 

Its  principal  constituent  is.  a  substance  resembling  albumen  or 
casein,  but  which  is  not  perfectly  identical  with  albuminate  of 
soda,  casein  or  ptyalin.  Bernard  calls  it  cliylopoine.  It  coagu- 
lates imperfectly  when  heated,  is  precipitated  by  acetic  acid,  but 
redissolves  slowly  in  excess  of  the  reagent,  especially  if  heat  be 
applied,  and  from  this  second  solution  it  is  precipitated  by 
ferrocyanide  of  potassium.  Nitric  acid  precipitates  it,  and,  if 
it  be  then  boiled,  especially  if  ammonia  be  added,  a  deep  yellow 
color  is  observed.  Chlorine  water  separates  it  in  grayish  flakes. 
Alcohol  throws  it  down,  but,  according  to  Bernard,  water  redis- 
solves it.     It  is  to  this  substance  that  the  secretion  owes  its 


INTESTINAL  DIGESTION.  143 

principal  chemical  and  physiological  properties.  Frerichs  found 
0.309^  in  the  pancreatic  juice  of  an  ass. 

There  are  also  found  in  this  secretion  a  hutter-like  fat,  extract- 
ive, and  some  mineral  substances,  consisting  chiefly  of  carbonate 
and  phosphate  of  lime  and  magnesia,  chloride  of  sodium,  and 
alkaline  phosphates  and  sulphates. 

Frerichs's  analysis  of  the  pancreatic  fluid  of  the  ass  is  as  fol- 
lows : — 

Water 

Solids 

Fat 

Alcohol  extract       .... 
Water  extract,  albuminous  (chylopoine) 

C  chlorides     ^ 
Alkaline^  phosphates  V  .         .         .  8.90 

(^  sulphates    J 
Carbonate  and  phosphate  of  lime  and  mag- 
nesia .......  1.20 


.  986.40 

.     13.60 

0.26 

0.15 

3.09 

1000.00      13.60 

Valentin  first  showed  that  this  secretion  possessed  the  power 
of  converting  into  sugar  the  amylaceous  matters  which  have 
escaped  the  action  of  the  saliva,  and  passed  into  the  duodenum. 
Bernard  and  Frerichs  have  confirmed  his  opinion,  and  have 
shown  that  this  secretion  possesses  this  property  in  a  higher 
degree  than  saliva. 

Bernard  has  advanced  the  opinion,  corroborated  by  numerous 
experiments,  that  the  pancreas  furnishes  the  means  of  digesting 
the  fats.  On  killing  a  rabbit,  shortly  after  giving  it  fat,  he 
found  the  absorbents  empty  as  far  down  as  the  duct  of  Wirsung, 
but,  below  that,  filled  with  milky  chyle.  In  another  experiment, 
he  tied  the  pancreatic  duct,  and  found  that  the  oil  remained  un- 
digested in  the  intestines.  He  took  the  fresh  juice  from  an 
animal,  mixed  it  with  fats,  and  found  that  it  formed  the  same 
chyle-like  emulsion  out  of  the  body  as  in  it.  These  experiments 
of  Bernard  have  been  confirmed  by  the  French  Academy.  They 
are  farther  confirmed  by  the  pathological  fact,  that  the  diseases 


144  DIGESTION. 

of  the  pancreas  are  attended  by  the  discharge  of  fatty  matters 
per  anum. 

On  the  other  hand,  Frerichs,  Lenz,  and  Bidder  and  Schmidt, 
have  been  unable  to  corroborate  these  experiments.  After 
tying  the  pancreatic  duct  in  cats  that  had  fasted  long,  and 
killing  them  in  from  four  to  eight  hours  after  the  meal,  they 
found  the  lacteals  injected,  and  the  receptaculum  chyli  distended 
with  milky  chyle.  Frerichs  tied  the  intestine  far  below  the 
entrance  of  these  ducts,  and  then,  on  injecting  oil  into  the  lower 
portion,  found  the  lacteals  in  due  time  filled  with  milky  chyle. 
Schmidt  and  Bidder,  experimenting  on  butter,  found  that  pan- 
creatic juice,  when  not  interfered  with  by  gastric  juice,  did  set 
free  butyric  acid,  but  that  in  the  presence  of  the  latter  fluid,  or 
of  any  acid,  no  such  change  took  place.  The  same  observers 
think  that  Bernard  was  led  into  error  by  not  killing  his  rabbits 
soon  enough.  They  found,  on  repeating  his  experiment  of  ad- 
ministering oil  to  rabbits,  that  when  the  animals  were  killed 
two  hours  afterwards,  milky  chyle,  rich  in  fat,  was  found  in  the 
lacteals  between  the  pylorus  and  the  biliary  duct.  Later,  the 
chyle  gradually  disappeared  from  the  upper  lacteals,  and  were 
found  in  those  lower  down  the  intestinal  tract. 

Most  of  Frerichs's  experiments  originated  in  a  misconception 
of  Bernard's  views.  He  understood  him  to  assert  that  a  change 
into  glycerine  and  fatty  acids  took  place  within  the  intestines ; 
whereas,  the  Frenchman  only  intimates  that  such  is  probably 
the  ultimate  disposition  of  fat,  and  asserts  that  this  change  takes 
place  out  of  the  body,  under  the  agency  of  the  pancreatic  juice  ; 
which  statement  we  find  confined  by  Bidder  and  Schmidt.  Fre- 
richs found  that  when  the  intestines  were  cut,  and  oil  injected 
into  either  end,  the  lacteals  proceeding  from  that  portion  which 
contained  the  bile  and  pancreatic  juice  were  far  fuller  than  those 
which  came  ofi"  from  the  lower  bowel. 

The  result,  therefore,  of  these  counter-experiments,  seems  to 
be  not  so  much  a  contradiction  of  Bernard's  results,  as  a  modi- 
fication of  them.  They  appear  to  indicate  that  his  statements, 
while  true  in  the  main,  are  rather  too  broad,  and  that  he  has 
not  given  sufficient  importance  to  the  action  of  the  bile,  and  of 
the  succus  entericus  upon  the  fatty  matters. 


INTESTINAL  DIGESTION.  145 

Frerichs  thinks  "  that,  as  the  decomposition  of  the  bile  is  very 
much  hastened  by  the  pancreatic  juice,  this  property  is  of  some 
importance  in  effecting  the  rapid  conversion  of  the  bile  into  sub- 
stances incapable  of  resorption." 

INTESTINAL  JUICE. 

Recent  researches  on  the  chemistry  and  physiology  of  the 
intestinal  juice  have  been  made  by  Frerichs,  Lehmann,  and  Bid- 
der and  Schmidt.  Frerichs  applied  ligatures  to  the  intestines  of 
animals,  so  as  to  exclude  food  and  all  the  secretions  which  are 
poured  into  the  intestinal  canal  from  above,  and  having  returned 
the  portions  of  intestine  included  in  the  ligature  into  the  abdo- 
men, and  allowed  some  hours  to  elapse,  he  killed  the  subjects  of 
his  experiments.  He  found  in  the  intestine  a  glassy,  transpa- 
rent, colorless,  and  tenacious  mass,  with  a  strong  alkaline  re- 
action. Lehmann  obtained  the  same  fluid  from  a  fistulous  open- 
ing in  a  man ;  and  Bidder  and  Schmidt  procured  it  from  similar 
openings  in  dogs. 

This  juice  does  not  mix  readily  with  water  ;  it  cakes  and  seems 
to  coagulate  when  treated  with  a  saline  solution,  while  the  por- 
tion soluble  in  water  behaves  like  mucus.  Frerichs  found  from 
2.2  to  2.6g  of  solid  constituents  in  this  juice,  of  which,  the  parts 
soluble  in  water  amounted  to  O.ST^,  the  fat  to  0.1952,  ^^^  the 
ash  to  0.842.     Lehmann  found  only  2.156g  of  solid  constituents. 

Frerichs  could  observe  no  digestive  action  Avhatever  in  the 
intestinal  juice,  but  in  this  he  differs  from  other  observers. 
Lehmann,  however,  discovered  that  it  possessed,  in  a  very  emi- 
nent degree,  the  power  of  transmuting  starch  into  sugar,  though 
he  did  not  think  it  exerted  any  digestive  influence  upon  the  pro- 
tein bodies,  especially  as  cubes  of  coagulated  albumen,  and^pieces 
of  flesh  introduced  below  the  fistula  in  his  subject,  passed  out  of 
the  rectum  unchanged.  Bidder  and  Schmidt,  however,  ascer- 
tained that  the  intestinal  juice  not  only  metamorphosed  starch 
as  rapidly  as  either  saliva  or  the  pancreatic  fluid  could,  but 
also  that  the  intestine  exerts  as  powerful  a  digestive  influence 
on  flesh,  albumen,  and  the  other  protein  bodies,  as  the  stomach. 
Bernard,  too,  attributes  the  same  property  to  the  intestinal  juice. 
10 


146  DIGESTION. 

He  thinks  that  the  mixed  fluids,  contained  in  the  bowels,  act 
the  part  of  a  universal  solvent  on  all  alimentary  materials  sub- 
jected to  their  influence. 

CONTENTS  OF  THE  INTESTINAL  CANAL  AND  EXCREMENTS. 

The  examination  of  the  contents  of  the  intestinal  canal  has 
not  led  to  any  very  certain  results.  The  mixture  is  so  hetero- 
geneous, consisting  of  imperfectly  digested  food,  indigestible 
matter,  and  the  various  secretions  already  described,  in  diff'erent 
stages  of  decomposition,  that  it  is  next  to  impossible  to  estimate 
the  source  whence  any  given  product  is  derived,  or  to  trace  a 
single  compound  through  its  various  metamorphoses. 

The  reaction  of  the  contents  of  the  bowels  is  acid  in  the 
duodenum  and  jejunum,  but  gradually  changes  and  commonly 
becomes  alkaline  in  the  colon.  Often,  however,  the  contents 
next  the  mucous  membrane  are  alone  alkaline,  the  central  por- 
tions being  strongly  acid.  This  reaction  is  partly  due  to  the 
liberated  resinous  acids  of  the  bile,  but  chiefly  to  lactic  acid,  the 
ultimate  product  of  the  metamorphosis  of  amylaceous  matters 
in  the  intestines.  These  resinous  biliary  acids  can  be  detected 
as  low  down  as  the  ileo-coccal  valve.  Sometimes  butyric  acid 
is  found  in  the  large  bowel. 

Grape  sugar  is  also  found  in  the  intestinal  canal.  It  is  the 
result  of  the  action  of  the  pancreatic  juice  upon  the  food.  A 
protein  body,  coagulable  by  heat,  has  also  been  detected. 
Lehmann  is  inclined  to  ascribe  this  to  the  transudation  of  some 
of  the  contents  of  the  bloodvessels ;  but  Frerichs  thinks  it 
results  from  a  true  digestion,  or  at  least  from  the  conversion  of 
albuminose  into  ordinary  albumen  by  the  bile.  Dextrin  is  rarely 
found,  and  only  very  small  quantities  of  the  peptones. 

Biliary  matters  are  always  found  in  the  alimentary  canal. 
They  have  been  discovered  in  the  gastric  contents  of  slaughtered 
animals  and  men  suddenly  killed.  The  lower  down  the  con- 
tents of  the  intestinal  canal  are  examined,  the  smaller  is  the 
quantity  of  the  resinous  acids  of  the  bile  which  can  be  detected. 
In  the  duodenum,  much  unchanged  bile  is  detected,  but  the 
acids  gradually  disappear,  till,  at  the  lower  portion  of  the  small 
intestines,  nothing  but  cholinic  and  fellic  acids  and  dyslysin  can 


INTESTINAL  DIGESTION.  147 

be  detected,  and  even  these  in  small  quantity.  In  the  large 
intestine,  even  these  have  disappeared,  and  nothing  remains  but 
a  little  ethereal  extractive.  Taurine  has  been  often  detected 
by  Frerichs  throughout  this  tube.  Fat  is  always  found,  and 
with  it  cholesterin.  The  hile-pigment  gradually  undergoes  the 
same  changes  in  the  intestinal  canal  as  are  observed  to  take 
place  during  the  putrefaction  or  decomposition  of  the  bile. 

The  microscope  detects  in  the  insoluble  matter,  shrunken, 
fissured,  and  lobulated  starch  granules;  muscular  fibres  in 
various  stages  of  disintegration ;  and  various  histological  vege- 
table elements,  such  as  chlorophyll-cells,  or  those  which  con- 
tain the  green  coloring  matter  of  plants,  parenchyma-cells, 
spiral  vessels,  and  sometimes  yeast-cells. 

The  gases  of  the  alimentary  tube  vary  in  their  composition 
and  origin.  In  the  stomach,  they  often  contain  little  in  addition 
to  atmospheric  air,  and  these  have  probably  originated  from 
the  gas  contained  in  the  saliva,  or  carried  in  with  the  food,  or 
from  atmospheric  air  swallowed  during  certain  respiratory  acts, 
the  inspiration  preceding  vomiting,  for  example.  Much  of  this 
gas  originates  from  the  fermentation  of  imperfectly  digested 
food.  If  this  be  acetous,  carbonic  acid  will  be  generated ;  if 
butyric,  hydrogen  will  be  developed.  In  100  volumes  of  gas 
taken  from  the  stomach  of  an  executed  criminal,  Magendie  and 
Chevreul  found  14  volumes  of  carbonic  acid,  11  of  oxygen, 
71.45  of  nitrogen,  and  3.55  of  hydrogen.  In  gas  taken  from 
the  stomach  twenty-four  hours  after  death,  Chevillot  found  in 
two  cases: — 

Carbonic  acid     . 
Oxygen 
Nitrogen    . 

100.  100. 

with  mere  traces  of  hydrogen. 

In  the  small  intestines,  there  is  usually  more  gas  than  in  the 
large.  In  these,  Magendie  and  Chevreul  found  no  oxygen,  but 
nitrogen  and  a  great  quantity  of  carbonic  acid  and  hydrogen. 
Chevillot  found  2  or  3^  of  oxygen  in  this  gas.     Sulphuretted 


25. 

27.8  volumes, 

8.2 

13. 

4( 

66.8 

59.2 

U 

148  DIGESTION. 

hydrogen  is  often  found  in  this  gas,  and  its  development  is 
favored  by  the  use  of  preparations  of  iron. 

In  the  large  intestine,  gaseous  accumulations  are  more  common, 
and  consist  chiefly  of  carbonic  acid,  nitrogen,  and  carburetted 
with  a  small  quantity  of  sulphuretted  hydrogen.  These  gases 
usually  proceed  from  putrefying  food  and  animal  juices,  though 
there  are  some  facts  which  seem  to  confirm  the  old  notion  of  an 
ccasional  secretion  of  gas  from  the  walls  of  the  intestine. 

Vomited  3Iatters. — These  vary  very  much,  in  accordance 
with  the  ingesta,  the  time  which  has  elapsed  after  taking  food, 
and  many  other  circumstances.  When  vomiting  occurs  shortly 
after  eating,  little  more  than  unaltered  food  is  rejected.  When 
the  food  has  remained  longer  in  the  stomach,  the  amylaceous 
matters  undergo  fermentation,  either  of  the  mucous,  the  acetous, 
the  lactic,  or  the  butyric  kind.  The  vomit  is  then  sharp  and 
acid,  in  common  parlance,  setting  the  teeth  on  edge,  except  in 
cases  of  mucous  fermentation,  when  the  rejected  matters  are 
alkaline.  In  yellow  fever,  in  cancer  of  the  stomach,  and  other 
gastric  hemorrhages,  black  or  coffee-ground  vomit  takes  place. 
This  has  been  satisfactorily  proved  to  consist  of  blood-corpuscles, 
altered  by  the  juices  of  the  stomach. 

In  ileus,  from  whatever  cause  produced,  we  have  an  inverted 
peristaltic  action  of  the  intestinal  tube,  and,  of  course,  find  its 
contents  in  the  matters  vomited.  Bile  is  always  thrown  up  during 
protracted  vomiting.  It  is  of  no  pathognomonic  importance, 
for  in  the  mechanical  compression  of  the  liver  and  the  gall- 
bladder, and  in  the  well-known  increase  of  secretion  from  the 
glands  connected  with  the  alimentary  canal  which  always  attends 
nausea  and  vomiting,  we  have  a  simple  and  true  explanation  of 
this  sort  of  bilious  vomiting. 

Goodsir  has  called  attention  to  the  fact  that,  under  certain 
circumstances,  which  are  not  well  understood,  a  microscopic 
alga,  or  infusorial  plant,  is  thrown  up  from  the  stomach.  This 
little  organism  is  made  up  of  square  quadripartite  cells,  from 
1- 300th  to  l-500th  of  a  line  in  diameter,  which  are  found  either 
singly  or  combined  in  little  plates.  They  resemble  packets 
tied  up,  and  from  this  resemblance  they  have  received  the  name 
sarcina.     Frerichs  has  studied  their  development  and  finds  that 


INTESTINAL  DIGESTION. 


149 


Fig.  20. 


they  originate  from  non-nucleated  cells,  isolated,  or  grouped 
in  twos.  These  cells  gradually  undergo 
a  constriction,  which  is  crossed  by  an- 
other at  right  angles,  till  they  appear  to 
be  divided  into  four  equal  parts.  Each 
of  these  squares  undergoes  the  same 
constriction,  growing  all  the  while,  till 
at  last  each  original  individual  expands 
into  a  large  plate,  intersected  by  rect- 
angular lines,  and  easily  divided  into 
separate  quadripartite  cells.  Lehmann 
thinks  that  it  is  identical  with  the  Meris- 
mopedia  punctata  described  by  Meyen. 

The  fluid  of  pyrosis  has  sometimes  been  found  to  be  alkaline, 
and  sometimes  acid.  Much  diversity  of  opinion  has  prevailed 
in  reference  to  it.  It  has  been  thought  by  some  to  be  derived 
from  the  stomach,  by  others  to  come  from  the  salivary  glands. 
Wright  long  ago  proved  that  it  often  originated  in  the  latter 
organs,  and  Frerichs  has  since  confirmed  the  observation.  The 
latter  chemist  found  that  the  vomited  fluid  contained  sulpho- 
cyanides,  that  it  digested  starch,  and,  indeed,  possessed  the 
other  properties  of  saliva. 

In  diabetes,  sugar  is  vomited.  The  gastric  glands  probably 
possess  the  same  power  of  separating  sugar  from  the  blood  in 
this  affection,  which  has  often  been  noticed  as  belonging  to  the 
salivary  gland. 

Excrements. — The  quantity  of  semisolid  brown  masses  dis- 
charged, during  twenty-four  hours,  from  the  rectum  of  an  adult, 
living  on  a  mixed  diet,  varies  at  from  4  to  6  ounces  troy.  As 
these  contain  about  25  per  cent,  of  solid  matter,  the  amount  of 
solids,  passing  away  in  the  feces,  is  from  1  to  1.5  ounces  a 
day. 

The  insoluble  portion  of  the  feces  consists  chiefly  of  various 
morphological  elements.  We  find  in  them  fragments  of  undis- 
solved muscular  fibres,  cartilage,  and  fibro-cartilage  cells,  elastic 
fibres,  and  the  various  vegetable  structures  already  noticed. 

We  find,  also,  fat,  crystals  of  cholesterin,  and  undecomposed 
food,  as  well  as  the  brown  bile-pigment,  epithelium-cells,  and 


150  DIGESTION. 

mucus-corpuscles.  Various  saline  particles  are  also  discovered 
by  the  microscope^  among  which  are  well-defined  crystals  of 
ammoniaco-magnesian  phosphate.  This  salt  was  supposed  by 
Schonlein  to  be  pathognomonic  of  typhus,  but  it  has  been  shown 
to  occur  in  perfectly  normal  feces.  In  typhus,  cholera,  and 
certain  forms  of  dysentery,  however,  it  is  increased  in  quantity, 
and  its  crystals  are  larger. 

Dr.  Percy  has  made  several  analyses  of  dry  feces,  which  are 
recorded  in  Simon  s  Animal  Cliemistry.  One  of  them,  of  the 
feces  of  a  man  eating  the  common  food  of  England,  we  give  : — 

Substances  soluble  in  ether  (brownish-yellow  fat)    .  11.95 

alcohol  of  .830     .         .         .  10.74 

"                  "         water  (brown  resinoid  matter)  11.61 

Organic  matter  insoluble  in  the  above  menstrua     .  49.33 

Salts  soluble  in  water            .....  4.76 

"     insoluble  in  water         .....  11.61 


100.00 


The  ultimate  analyses  of  the  same  feces  gave,  carbon,  46.20; 
hydrogen,  6.72;  nitrogen  and  oxygen,  30.71;  ash,  16.37  in  the 
100  parts.  Enderlin  examined  the  ash,  and  found  it  to  con- 
sist of 


1.367  \  Soluble  in 
2.633  J     water. 

Insoluble 
2.090  I 

V        in 
4.530  f 

water. 
7.946J 


Chloride  of  sodium  and  alkaline  sulphates 

Bibasic  phosphate  of  soda 

Phosphates  of  lime  and  magnesia 

Phosphate  of  iron 

Sulphate  of  lime 

Silica         ..... 

This  corresponds  with  Dr.  Percy's  statement,  but  Lehmann's 
results  differ  widely  from  these.  He  found  in  the  ash  of  feces, 
23.067g  of  soluble  salts.  It  is  remarkable  that  potash  pre- 
dominates considerably  over  soda.  It  is  also  worthy  of  observa- 
tion that  there  is  always  a  relative  excess  of  magnesia  over  lime 
in  the  feces,  as  compared  with  the  food. 

The  odor  of  the  feces  has  been  thought  by  some  to  depend 
upon  the  secretion  of  the  glands  of  the  colon,  and  by  others,  to 


INTESTINAL  DIGESTION.  151 

be  due  to  the  decomposition  of  bile.  Liebig,  however,  has  as- 
certained that,  by  fusing  gehitinous  and  albuminous  substances 
with  potash,  supersaturating  with  sulphuric  acid  and  distilling, 
a  fluid  containing  acetic  and  butyric  acid,  and  possessing  the 
peculiar  fecal  odor  in  an  eminent  degree,  passes  over.  The 
odor  varies  with  the  article  employed,  but,  in  this  way,  every 
variety  of  fecal  odor  may  be  developed.  The  action  of  caustic 
potash  at  this  high  temperature,  being  only  an  imperfect  oxida- 
tion, confirms  Liebig's  idea  that  the  feces,  like  the  soot  in  a 
chimney,  are  the  product  of  the  imperfect  oxidation  of  the  food. 
He  calls  attention  to  the  fact  that  their  odor  differs  from  that 
of  ordinary  putrefaction  or  fermentation,  and  that,  when  they 
enter  into  fermentation  themselves,  out  of  the  body,  they  lose 
this  characteristic  smell. 

The  small  intestines  in  the  foetus,  at  the  sixth  month,  contain 
a  bright-yellow  mass,  composed  of  fat,  salts,  mucus,  epithelium, 
and  biliary  matters.  After  the  seventh  month,  the  meconium 
appears.  This  substance  contains  cholesterin  and  other  fats, 
epithelium  and  mucus,  and  a  nitrogenous  body.  Lehmann  could 
not  detect  bile-pigment  or  biliary  acids,  but  Simon  detected  a 
notable  quantity  of  both. 

The  bright-yellow,  semifluid  excrements  of  infants  were  found 
by  Simon  to  contain  a  large  amount  of  fat,  much  coagulated 
casein  and  bile-pigment. 

A  green  color  in  the  feces  was  formerly  supposed  to  be  always 
due  to  bile-pigment,  though  of  late  the  presence  of  this  coloring 
matter  in  the  stools  has  been  totally  denied.  As  usual,  the 
truth  is  found  to  lie  between  the  two  extremes.  The  green  color 
may  be  present  without  any  unchanged  bile-pigment,  but  that 
pigment  is  sometimes  found  in  green  stools.  In  calomel  stools 
sulphuret  of  mercury  is  always  present,  and  this  has  given  the 
green  tint  observed  in  experiments  on  intestinal  mucus,  which 
has  led  some  persons  to  deny  or  doubt  that  this  remedy  stimu- 
lates the  secretion  of  bile.  But  bile  is  also  present,  and  may  be 
recognized  by  Pettenkofer's  test.  Farthermore,  Buckheim  has 
ascertained,  by  observing  fistulous  openings  in  the  biliary  ducts, 
that  calomel  actually  increases  the  amount  of  this  secretion. 

Iro7i  also  communicates  a  green  color  to  the  feces,  especially 


152  DIGESTION. 

"when  it  is  taken  in  chalybeate  waters.  These  stools,  however, 
contain  no  bile,  according  to  Lehmann,  but  owe  their  green  tint 
to  sulphuret  of  iron.  That  this  substance  is  capable  of  pro- 
ducing this  color  may  be  shown  by  a  very  simple  experiment. 
Add  a  proto-salt  of  iron  to  albumen ;  dissolve  the  precipitate  in 
an  alkali,  and  add  to  the  solution  an  alkaline  sulphuret.  No 
precipitate  takes  place,  but  the  liquid,  till  now  colorless,  assumes 
an  intense  "steel-green"  tint.  Many  vegetable  matters  also 
stain  the  feces  green. 

The  process  of  digestion  commences  in  the  mouth,  as  soon  as 
the  food  has  been  introduced.  There,  the  alimentary  substances 
are  mixed  with  the  salivary  ferment,  which  commences  the 
transmutation  of  starch  into  sugar.  There,  too,  the  particles  are 
comminuted  so  as  to  facilitate  the  action  of  the  digestive  fluids. 
There  also  they  are  mixed  with  atmospheric  air,  which  furnishes 
the  oxygen,  so  important  to  their  farther  transformation. 

In  the  stomach,  the  albuminous  flood  is  digested  and  converted 
into  peptones,  which  are,  in  great  measure,  directly  absorbed. 
Probably,  all  the  sugar  that  is  formed  is  also  taken  up  and  car- 
ried ofl"  by  the  gastric  radicles  of  the  portal  vein  to  the  liver, 
there  to  undergo  the  metamorphoses  already  glanced  at.  The 
fat,  however,  is  only  released  by  the  digestion  of  the  membranes 
which  have  enveloped  it,  and  the  farinaceous  articles  of  food  are 
little,  if  at  all,  changed. 

In  the  intestines,  the  remaining  changes  are  effected.  There 
the  insoluble  and  innutritions  portions  of  the  food  are  separated 
from  the  soluble  and  nutritious  parts.  The  fat  is  there  reduced 
into  an  emulsion,  and  the  remaining  amylaceous  substances 
undergo  their  final  changes.  When  the  health  is  perfect,  and 
the  diet  has  been  in  proper  quantity,  nothing  is  finally  rejected 
but  those  substances  which  are  not  fit  to  be  taken  up. 

Thus,  digestion  is  a  complex  process,  requiring  a  thorough 
examination  of  all  the  cavities  of  the  alimentary  canal,  since 
it  is  performed  in  them  all,  and  not,  as  was  formerly  believed, 
accomplished  in  the  stomach  alone.  As  the  mouth  forms  a  sub- 
ject of  special  study,  the  digestive  processes  there  carried  on  will 
be  considered  in  the  description  of  that  cavity,  to  which  we  now 
proceed. 


BOOK  III. 

THE  CHEMISTRY  OF  THE  MOUTH. 


CHAPTER  I 

THE  TEETH. 


It  is  essential  to  every  one  who  would  deal  properly  with 
these  beautiful  organs,  that  he  should  understand  not  only  their 
anatomical  structure,  but  also  their  chemical  relations  to  the 
various  substances  which  surround  them.  Such  knowledge  as 
this,  of  course  comprises  the  chemical  constitution  of  the  teeth 
themselves  and  of  those  fluids  which  constantly  bathe  them. 

A  consideration  of  the  minute  anatomy  of  the  teeth,  does 
not,  of  course,  fall  within  the  scope  of  a  volume  like  the  present; 
yet,  as  the  chemical  composition  of  the  different  components  of 
these  organs  varies  very  considerably,  a  glance  at  their  struc- 
ture is  necessary.  Suffice  it  to  say,  that  three  distinct  ana- 
tomical histological  elements  can  be  demonstrated  in  the  teeth; 
the  dentine  or  ivory,  which  consists  of  cylindrical  and  branching 
tubuli,  and  composes  the  bulk  of  every  tooth ;  the  enamel^  which 
coats  the  exposed  surfaces  of  these  organs,  and  is  arranged  in 
hexagonal  prisms ;  and,  finally,  the  cementum  or  crusta  j^etrosa, 
which  contains  lacunae,  and  corresponds  in  all  essential  particu- 
lars with  bone.  In  a  perfectly  healthy  state  of  the  teeth  and 
gums,  the  enamel  is  the  only  one  of  these  portions  which,  in 
man,  comes  in  contact  with  the  fluids  of  the  mouth ;  but  when, 
from  any  cause,  the  gums  have  receded,  or  the  enamel  has  been 
Avorn  away,  the  dentine  is  exposed  to  the  same  agents  which 
should  only  operate  upon  the  enamel.     The  cementum  or  criista 


154  THE  CHEMISTRY  OF  THE  MOUTH. 

petrosa  is  far  removed  from  these  influences,  lying  at  the  bottom 
of  the  fang.  All  these  substances,  of  course,  consist  of  animal 
membranes,  holding  earthy  matters.  A  dilute  mineral  acid  will 
dissolve  out  the  calcareous  salts,  leaving  the  animal  matter 
behind.  It  will  then  be  observed  that  the  enamel  contains  the 
least  organic  matter,  the  dentine  considerably  more,  and  the 
cementum  most  of  all. 

This  will  be  seen  by  the  following  table  from  Von  Bib/a  : — 

INCISORS  OF  ADULT  MAN. 

Dentine.       Enamel.  Cementum. 

Organic  matter    .         .         28.70           3.59  29.27 

Earthy  matter     .         .         71.30         96.41  70.73 


100.00       100.00       100.00 

In  this  table,  the  cementum  approaches  so  nearly  to  the  den- 
tine in  chemical  composition  that  there  could  hardly  be  said  to 
be  any  difference  between  them. 

Lassaigne,  however,  gives  an  analysis  of  cementum  which 
differs  widely  from  the  above  by  Von  Bibra.     He  finds  in  it — 

Organic  matter  .....         42.18 

Phosphate  of  lime       .         .         .  53.84 1      ryj  oq 

Carbonate  of  lime      .         .         .  3.98 


100.00 


Berzelius's  analysis  of  dentine  corresponds  very  closely  with 
Von  Bibra's.     It  is  as  follows  : — 

Cartilage  and  vessels  ....  28.0 

Phosphate  of  lime  with  fluoride  of  calcium  64,3^ 
Carbonate  of  lime       ....  5.3 

Phosphate  of  magnesia        ...  1 

Soda  with  chloride  of  sodium       .  .  l-lj  ^^-^ 

Loss  ......  3 


100.0 


Pepys  obtained  the  same  amount  of  organic  matter,  but  less 
earthy  matter  than  Berzelius,  and  a  large  amount  of  water.    He 


THE  TEETH.  155 

has,  however,  associated  tuater  and  loss,  so  that  it  is  difficult  to 
determine  what  his  actual  results  were. 

Lassaigne  found  that  the  animal  matter  in  the  teeth  gradually 
diminished  as  age  advanced.     We  subjoin  his  table  : — 


Orgfinic 

Phosphate 

Carbonate 

matter. 

of  lime. 

of  lime. 

Tooth  of  a  child  1  day  old 

35.00 

51.00 

14.00 

"         "       "    aged  6  yrs. 

28.57 

60.01 

11.42 

"      of  an  adult  man 

29.00 

61.00 

10.00 

"      of  a  man  aged  81 

years 

33.00 

66.00 

1.00 

Berzelius's  analysis  of  enamel  is  as  follows  : — 

Membrane,  alkali,  and  water         .          .          .  2.0 

Phosphate  of  lime  with  fluoride  of  calcium     .  88.5 

Phosphate  of  magnesia          ....  1.5 

Carbonate  of  lime         .....  8.0 


100.0 


For  the  sake  of  a  more  extended  comparison  of  the  composi- 
tion of  the  three  organic  elements  of  the  teeth,  we  subjoin  Von 
Bibra's  analysis  of  the  incisors  of  an  ox : — 

Dentine.       Enamel.        Cement. 
Phosphate  of  lime,  with  a 
trace  of  fluoride  of  cal- 


cium 

59.57 

81.86 

58.73 

Carbonate  of  lime 

7.00 

9.33 

7.22 

Phosphate  of  magnesia 

0.99 

1.20 

0.99 

Salts  .... 

0.91 

0.93 

0.82 

Chondrin  (glutin  ?) 

30.71 

6.66 

31.31 

Fat     . 

0.82 

0.02 

0.93 

100.00      100.00       100.00 

By  a  comparison  of  two  of  Von  Bibra's  analyses,  it  would 
appear  that  the  teeth  of  women  contain  more  earthy  and  less 
organic  matter  than  those  of  men;  though,  it  must  be  con- 
fessed, no  positive   deductions  can  be   drawn  from   so  limited 


156 


THE  CHEMISTRY  OF  THE  MOUTH. 


a  number  of  observations.     The  following  is  the  analysis  of  a 
molar  tooth  of  a  woman  twenty-five  years  of  age  : — 


Enamel.     Dentine  and  Cementum. 


Phosphate  of  lime,  with 

fluoride  of  calcium 

81.63 

67.54 

Carbonate  of  lime  . 

8.88 

7.97 

Phosphate  of  magnesia 

2.55 

2.49 

Salts      . 

0.97 

1.00 

Cartilage 

5.9T 

20.42 

Fat        .         .         . 

a  trace. 

0.58 

100.00 


100.00 


The  corresponding  analysis  of  the  molar  tooth  of  an  adult 
man  is  here  subjoined  : — 


Enamel. 

Osseous  portion. 

Phosphate  of  lime,  with  a 

I  little 

fluoride  of  calcium 

89.82 

66.72 

Carbonate  of  lime    . 

4.37 

3.36 

Phosphate  of  magnesia    . 

1.34 

1.08 

Salts       . 

88 

0.83 

Cartilage 

3.39 

27.61 

Fat 

0.20 

0.40 

100.00 


100.00 


A  very  slight  consideration  of  the  above  analyses  will  show 
that  all  powerful  acids  will  easily  decompose  the  teeth,  whether 
in  or  out  of  the  body.  The  peculiar  and  very  unpleasant  sen- 
sation of  "teeth  set  on  edge,"  is  induced  in  these  organs  when- 
ever any  strong  acid  is  brought  in  contact  with  them,  as  they 
well  know  who  have  ever  been  so  unfortunate  as  to  have  met 
with  such  an  accident.  The  same  sensation  is  also  often  pro- 
duced by  the  acid  contents  of  the  stomach  rejected  in  the  act  of 
vomiting. 

Not  only,  however,  have  the  mineral  acids  the  power  of  dis- 
solving out  the  earthy  matter  of  these  organs,  but  many  organic 
acids  possess  the  same  property.  The  acids  already  spoken  of 
as  resulting  from  the  decomposition  of  food,  whether  amylaceous 


&ALIVA.  157 

or  albuminous,  can  dissolve  the  calcareous  salts  which  make  up 
the  inorganic  portion  of  the  teeth. 

The  author  has  been  engaged  in  a  series  of  experiments  upon 
these  organs  to  determine  the  relative  activity  of  these  different 
acids  ;  but,  as  yet,  they  have  not  been  sufficiently  numerous, 
nor  have  they  been  re-examined  with  sufficient  care  to  warrant 
him  in  laying  them  before  the  public,  at  this  stage  of  his  inves- 
tigations. This  much,  however,  he  may  say,  that  so  far  as  he 
has  examined  the  subject,  the  different  acids  generated  during 
the  putrefaction  or  fermentation  of  vegetable  or  animal  food, 
are  fully  capable  of  disorganizing  the  teeth.  They  convert  the 
enamel  into  a  white,  opaque,  very  friable  substance,  almost  en- 
tirely devoid  of  lustre,  and  soften  the  dentine  so  as  to  leave  little 
but  its  animal  matter.  They  materially  diminish  the  weight  of 
the  teeth,  in  consequence  of  the  earthy  matter  they  have  dis- 
solved, which  can  be  precipitated  from  the  solutions  by  the 
ordinary  reagents.  Not  satisfied  with  the  examination  of  the 
individual  acids,  the  author  has  also  mixed  finely  comminuted 
food  with  the  fluids  of  the  mouth,  and  subjected  the  teeth  to  the 
action  of  the  mixture  while  fermentation  went  on.  The  same 
results  precisely  were  arrived  at  in  this  instance  as  when  experi- 
menting with  the  separate  acids. 


CHAPTER    II. 

SALIVA. 

The  importance  of  a  thorough  knowledge  of  the  fluids  of  the 
mouth  can  hardly  be  overrated.  They,  of  necessity,  mingle 
themselves  with  all  our  ingesta,  and  exert,  in  this  way,  a  power- 
ful influence  over  digestion.  Some  of  them  hold  important  phy- 
siological relations  with  this  function,  and  all  of  them  may,  in 
disease,  materially  interfere  with  its  proper  performance.  None 
of  them  has  a  higher  claim  upon  the  attention  of  the  physiologist 


158  THE  CHEMISTRY  OF  THE  MOUTH. 

or  the  pathologist  than  the  saliva,  which  it  is  our  purpose  to 
examine  in  the  present  chapter. 

The  name  saliva  has  been  as  copious  a  theme  for  debate 
among  the  etymologists  as  the  substance  itself  has  been  among 
the  chemists.  Some  have  derived  it  from  sal,  salt,  because  of 
the  abundance  of  salts  it  contains,  and  for  a  variety  of  other 
reasons,  which  it  would  require  too  much  time  to  particularize. 
Others  will  have  it  to  be  a  corruption  of  (jaTtfuw;  and,  if  they  are 
right  in  their  etymology,  it  certainly  is  a  degradation  of  this 
word,  which  was  originally  applied  to  the  roll  of  the  yesty  waves 
of  a  troubled  sea.  Others  take  it  from  salvando,  because  it  was 
thought  to  save  life  by  curing  a  variety  of  diseases  ;  and  others, 
again,  from  saliendo,  because  it  leaps  into  the  mouth,  from  many 
little  tubes,  like  the  jets  from  a  fountain.  Some,  again,  think 
it  a  corruption  of  the  Greek  aiaxov,  which  is  itself  involved  in 
similar  etymological  difficulties.  Dr.  Samuel  Wright,  of  Edin- 
burgh, is  particularly  learned  upon  this  subject,  and  to  his  ad- 
mirable papers  in  the  Lancet,  which  we  have  very  freely  used, 
we  refer  the  reader  who  is  inquisitive  about  this  little  piece  of 
etymology. 

This  name  has  been  applied  indiscriminately  to  the  secretions 
furnished  by  the  various  glands  which  discharge  their  contents 
into  the  cavity  of  the  mouth,  the  xtarotid.  the  submaxillary,  and 
the ^ublingyial^ though  we  shall  presently  have  occasion  fo  show 
that  these  different  organs  do  not  produce  a  homogeneous  liquid. 
The  common  saliva,  besides  being  thus  made  up  of  different 
fluids,  is  mingled  also  with  the  buccal,  lingual,  and  labial  mucus. 
Various  methods  have  been  devised  to  obtain  it  perfectly  pure. 
The  most  certain  of  these  is  probably  to  procure  it  from  patients 
suffering  under  salivary  fistula,  though  it  has  been  doubted 
whether  this  can  be  taken  as  a  normal  secretion.  Wright's  plan 
was  first  to  rinse  the  mouth  with  cold  water ;  then,  having 
depressed  the  lower  jaw,  to  tickle  the  fauces  so  as  to  excite 
nausea  without  vomiting.  This  brings  it  out  in  a  full  stream, 
unmixed,  as  he  thinks,  with  any  foreign  matter.  The  admixture 
of  extraneous  substances  with  the  liquid  thus  obtained  cannot, 
indeed,  be  great,  but  that  some  mucus  must  get  access  to  it  is 
manifest  upon  a  moment's  reflection.      Epithelium  scales  and 


SALIVA. 


159 


mucus  from  the  ducts  must  always  be  present,  in  whatever  way 
it  may  be  obtained,  and  to  this  we  probably  owe  the  globules, 
which  the  microscope  detects  in  such  quantities  in  the  saliva. 
The  time  at  which  this  fluid  is  obtained  for  examination,  is  by 
no  means  unimportant.  Wright  suggests  that  it  be  collected 
from  a  healthy  person  after  a  fast  of  about  three  hours. 

Healthy  saliva  is  described,  by  the  last-named  observer,  as  a 
"  limpid  fluid,  having  a  faint-blue  tinge,  and  a  slight  degree  of 
viscidity.    It  is  perfectly  uniform,  in  consistence,  and  unobscured 
by   frothiness    or   flocculi.      It 
possesses  a  faint  sickly  odor,  sui  ^S*     ' 

generis,  due  to  its  constituent, 
'ptyalin;  this  odor  is  strengthen- 
ed by  heat,  and  by  most  acids, 
but  alkalies  diminish  and  destroy 
it."  Most  observers  assert  that 
it  is  always  totally  tasteless, 
but  Wright  insists  that  it  has  a 
manifest  sapor.  He  acknow- 
ledges that,  to  the  individual 
secreting  it,  the  freshly  formed 
fluid  is  tasteless,  but  asserts 
that   the   saliva   of   another    is 

always  sapid,  and  that  a  man  may  retain  his  own  in  his  mouth 
until  it  shall  possess  taste  which  becomes  very  distinct  if  it  is 
collected  in  a  vessel  and  then  applied  to  the  tongue.  Lehmann 
and  Jacubowitsch,  the  most  recent  writers  on  this  subject,  are 
at  variance  with  Wright  upon  this  point,  and  suggest  that  the 
saliva  he  experimented  on  may  have  been  a  little  stale,  a  matter 
of  some  consequence  in  a  fluid  so  prone  to  decomposition. 

The  quantity  of  this  fluid,  which  is  secreted  in  the  course  of 
a  day,  has  never  been  exactly  ascertained,  and  must  be  subject 
to  great  variation.  The  quantity  of  fluid  ingested,  the  amount 
of  motion  in  the  muscles  of  mastication,  the  character  of  the 
substances  taken  as  food,  all  must  influence  it.  Movements  of 
the  jaws,  stimulating  condiments,  even  the  thought  of  food 
increases  its  flow.  Mitscherlich  obtained  from  a  patient  laboring 
under  salivary  fistula,  in  the  duct  of  Steno,  about  2J  ounces  in 


160  THE  CHEMISTRY  OF  THE  MOUTH. 

24  hours.  At  the  same  time  he  ascertained  that  the  whole 
amount  secreted  was  about  six  times  the  product  of  this  single 
gland.  It  is  probable,  therefore,  that  this  patient  was  making 
about  20  ounces  of  saliva  in  24  hours. 

Burdach  calculates  the  amount  at  8.2  ounces  troy ;  Valentin 
assumes  it  at  from  7  to  10.2;  Donn^  fixes  it  at  12.5,  and  Thomp 
son  at  only  6.7  ounces  troy.  Jacubowitsch  found  in  dogs,  that, 
in  an  hour,  the  two  parotids  secreted  49.2  grammes,  the  sub- 
maxillaries 38.83,  and  the  rest  of  the  glands,  with  the  mucous 
membrane,  24.84  grammes.  Lehraann  observes  that  these  ob- 
servations of  Jacubowitsch  are  not  of  much  value,  because  he 
does  not  state  the  size  or  weight  of  the  dog  experimented  on. 
The  important  fact  ascertained  by  this  observer  is,  that  though 
the  actual  amount  of  the  secretion  may  vary,  because  the  water 
varies,  the  solid  constituents  separated  by  the  three  sets  of 
glands  are  very  much  the  same ;  the  solids  hourly  discharged 
by  each  pair  of  glands  amounting  to  about  0.232  of  a  gramme 
(3.581  grains),  of  which  0.080  (1.235  grains)  is  organic,  and 
0.152  (2.346  grains)  in  organic  matter. 

Bidder  and  Schmidt  have  made  experiments  on  dogs  which 
are  not  open  to  the  objections  urged  by  Lehmann.  From  one  of 
the  ducts  of  Wharton  of  a  dog  weighing  about  35  pounds,  they 
obtained,  in  an  hour,  87.048  grains  of  saliva,  so  that  the  two 
submaxillary  glands  must  have  secreted  174.096  grains  in  the 
same  time.  From  one  of  the  ducts  of  Steno,  they  obtained,  in 
the  same  time,  135.265  grains  of  clear,  limpid  secretion,  so  that 
the  two  were  separating  270.53  grains  an  hour.  The  flow  of 
saliva  was  stimulated  by  occasionally  applying  a  feather,  moist- 
ened with  acetic  acid,  to  the  mucous  membrane  of  the  mouth. 
Assuming,  now,  that  a  man  weighs  140  pounds;  that  is,  four 
times  as  much  as  the  dog,  and  that  the  secretion  varies  directly 
with  the  weight,  he  will  secrete  from  his  submaxillaries  about 
1.45,  and  from  his  parotids  about_2.25  ounces  troy  in  an  hour. 
This  would  make  the  entire  daily  secretion  amount  to  more  than 
6  pounds.  Bidder  and  Schmidt  think  the  actual  amount  to  be 
:aiimiJ!uhalf-thia_45ga_antity.  By  actual  experiment,  they  found 
that  a  man  secreted  from  5.2  to  3.9  ounces  troy  in  an  hour, 


SALIVA.  161 

which  would  make  the  daily  yield,  deducting  for  sleep,  about  3 
pounds. 

These  estimates  are,  of  course,  approximative  only,  the  actual 
secretion  varying  much,  with  extraneous  circumstances,  as  we 
shall  hereafter  show. 

The  specific  gravity  of  saliva  is  another  point  upon  which 
observers  are  not  unanimous.*  The  discrepancies  here  are 
very  great,  and  are  partly  due,  undoubtedly,  to  the  greater  or 
less  admixture  of  mucus  with  the  fluids  tested  by  different  au- 
thors. Wright's  experiments,  however,  which  are  entitled  to 
the  utmost  respect  from  their  number,  having  been  made  upon 
more  than  five  thousand  individuals,  and,  from  the  accuracy  and 
candor  of  their  author,  show  that,  even  in  perfect  health,  the  den- 
sity of  saliva  varies  greatly,  in  consequence  of  idiosyncrasy,  the  \ 
nature  of  the  ingesta,  and  a  variety  of  other  circumstances.  He  1  > 
found  it  always  denser  after  a  meal  than  before  it,  in  the  evening  l/^ 
than  early  in  the  day.y(lt  is  "  CQmmonly  thickened  by  an*" 
abundant- -use  of  .animal  diet,iby.fatty  food,  especially,  QJid  by 
oily,  fish.. r^ Oysters  and  vegetable  diet_ produce  an  opposite 
e^kci^-i-^  tried  the  specific  gravity  of  the  saliva  in  a  healthy 
jman  for  a  week,  and  found  its  extremes  to  be  1.0079  and  1.0085. 
rthen  kept  him  upon  vegetable  diet  "and  water  for  a  week,' 
during  which  time  the  lowest  sp.  gr.  of  his  saliva  was  1.0039, 


and  the  highest  1.0041,. X^roughout  the  following  week  he 

took  nothing  but  animal  food  and  water,  with  four  ounces  of 

,  bread  daily ;  and  the  extremes  of  the  sp.  gr.  of  his  saliva  were 
1.0098  and  1^0176. 'VAll  alcoholic  stimulants  have  a  tendency 

>Jtp_J;h.ickeii-the  saHva-^yand,  in  large  quantities,  they  not  onlyi 
alter  its  consistence,  but  materially  diminish  its  activity.  Moralv 
emotions,  variations  in  the  state  of  the  weather,  electrical  con-| 
ditions  of  the  atmosphere,  light,  sound,  and   other   contingent 

*  The  following  are  some  of  the  estimates  of  different  authors.  Ilaller 
states  it  at^l.045  ;  Lamure  at  1.119 ;  Siebiild  at  1.080;  Xljomson  at  1.0038; 
Tiedemannana'Gmelin  at  1.0043;  Mitscherlich  at  1.0061„9,nd  1.0088; 
GTolding  Bird  at  1.0091  :  and  Wright  at  1.0079.  Lelimann  reckons  it  at 
from  1.004  to  1.006,  and  says  it  rises  during  health  to  1.009,  or  sinks  to 
1.002.  Jacubowitscli  makes  it  1.0026  before  filtration,  and  1.0023  after- 
wards. 

11 


162  THE  CHEMISTRY  OF  THE  MOUTH. 

circumstances,  exert  a  remarkable  influence  upon  the  secretion 
of  saliva,  and  also  upon  its  specific  gravity.  Hence  the  dif- 
ficulty of  making  accurate  observations  concerning  it.^_^  Lch- 
mann  attributes  the  higher  density  which  Wright  obtained^ 
the  greater  use  of  animal  food  by  the  English. 

Its  reaction  has  also  been  a  subject  of  discussion.  Wright 
believes  that  alkalinity  is  essential  to  the  proper  performance  of 
the  physiological  function  of  the  saliva.  He  found  the  alkalies 
to  vary  from  0.95  to  0.303  per  cent.,  a  proportion  which  may, 
however,  be  considerably  increased.  If,  at  any  time,  it  should 
exceed  one  per  cent,  he  regards  it  as  an  evidence  of  disease.* 
He  observed  a  remarkable  connection  between  this  secretion  and 
the  semen,  a  fact  of  no  little  interest,  if  we  connect  with  it  the 
well  known  pathological  sympathy  between  the  parotid  gland 
and  the  testicles  in  mumps.  After  coitus  in  dogs  the  alkalinity 
of  the  saliva  was  notably  diminished,  and  in  both  man  and 
animals  it  is  generally  increased  by  abstinence  from  sexual  in- 
tercourse. It  is  also  increased  during  digestion  and  diminished 
in  fastincj.  In  the  latter  state,  the  saliva  sometimes  becomes 
acid,  especially  if  the  abstinence  be  protracted,  but  in  moderate 
fasting  (e.  g.  from  6  to  12  hours),  Wright  says  the  fluid  may 
become  neutral,  but  should  never  be  acid.  When,  from  admix- 
ture of  mucus  or  other  causes,  it  exhibits  a  reaction  of  this 
character,  he  suggests  that  some  spirit  or  pepper  be  taken  in  the 
mouth,  under  the  stimulus  of  which,  in  a  healthy  person,  the 
quantity  of  alkali  is  always  very  much  increased.  He  says  he* 
has  known  the  proportion  of  alkali  to  be  increased  during  the 
space  of  a  quarter  of  an  hour  from  2  to  1.9  per  cent.  by||he 

*  From  Wright's  method  of  stating  this,  it  is  manifest  that  he  supposes 
the  alkaline  reaction  of  the  saliva  to  depend  upon  the  presence  of  free  soda; 
but,  as  Lehmann  remarks,  in  the  saliva  of  graminivorous  animals  there  is 
always  much  potash,  and  also  a  large  quantity  of  lime,  which  is  expelled 
from  its  combination  with  non-acid  organic  substances  by  the  weakest 
acids,  even  by  carbonic  acid.  Now,  as  it  requires  about  1.28  of  sulphuric 
acid  to  neutralize  one  part  of  soda,  we  can  easily  make  the  statement  in  a 
manner  which  shall  express  the  facts  without  committing  us  to  any  theory. 
This  would  be,  that  it  usually  requires  from  .122  to  .388  parts  of  sulphuric 
acid  to  neutralize  100  of  saliva,  and  that,  should  this  amount  increase  to 
1.28,  we  may  suspect  disease. 


SALIVA.  163 

local  application  of  an  irritant.  Slo"wness  of  digestion  from  the 
presence  of  much  fattj  matter,  alcohol  or  vinegar  in  the  stomach 
is,  in  like  manner,  accompanied  by  a  decided  increase  in  the 
quantity  of  alkali.  Frerichs  found  that  in  a  man  smoking 
tobacco,  the  quantity  of  alkali  was  so  much  diminished,  that  it 
required  but  .15  gramme  sulphuric  acid  to  neutralize  100 
grammes  of  saliva. 

Mitscherlich  was  the  first  to  isolate  the  saliva  of  one  of  the 
glands.  He  examined  the  fluid  collected  from  the  parotid  at  a 
fistulous  opening  in  the  duct  of  Steno.  Since  his  time  it  has 
been  examined  by  Vansetten  and  Garrod ;  and  Magendie  and 
Claude  Bernard  have  investigated  the  fluids  of  the  difi'erent 
larger  glands,  which  they  obtained  from  their  own  persons,  by 
introducing  tubes  into  the  diff"erent  ducts.  These  same  ob- 
servers, together  with  Jacubowitsch,  Lehmann,  and  Bidder  and 
Schmidt,  have  made  the  same  investigations  upon  the  saliva  in 
the  lower  animals.  From  these  experiments  it  is  manifest  that 
the  secretions  furnished  by  the  different  glands  difler  widely 
from  one  another  in  chemical  composition  and  in  physiological 
use.  That  from  the  parotid  and  sublingual  is  clear,  limpid,  and 
thin,  while  that  from  the  submaxillary  is  thick  and  viscid,  re- 
sembling simple  syrup  both  in  color  and  consistence. 

The  specific  gravity  of  the  parotid  saliva  is  stated  by  Golding 
Bird  at  1.0075.  In  dogs,  Jacubowitsch  found  it  to  vary  from 
1.004  to  1.0047;  and  in  horses,  according  to  Lehmann,  it 
ranges  from  1.0051  to  1.0074. 

Jts  reacdon  jsusuallyalkaHne  darjng^^  acid  when  fast- 

ing This  statement,  which  was  first  made  by  Mitscherlich,  has 
been  confirmed  by  Marshall  and  Garrod.  These  latter  ob- 
servers are  inclined  to  attribute  this  to  the  rapidity  of  the  dis- 
charge during  a  meal,  and  the  slowness  with  which  the  secretion 
is  formed  at  other  times.  They  found  that  ordinarily  but  two 
or  three  drops  were  discharged  by  one  parotid  gland  in  a  quarter 
of  an  hour,  and  that  this  was  acid  ;  but  that  in  half  a  minute 
after  a  morsel  had  been  taken  into  the  mouth,  the  reaction  was 
neutral,  and,  within  the  minute,  alkaline.  This  continued  till 
about  twenty  minutes  after  the  meal,  when  it  again  became  acid. 
This  is  accounted  for  by  the  fact  of  the  general  acidity  of  the 


164  THE  CHEMISTRY  OF  THE  MOUTH. 

mucous  surfaces  of  the  mouth,  which  is  sufficient  to  overpower 
the  feeble  alkalinity  of  the  saliva,  when  secreted  in  small  quan- 
tity. When  the  flow,  however,  is  increased,  the  saliva  more 
than  neutralizes  the  mucus,  and  hence  we  have  the  alkaline 
reaction.  The  mucus,  in  cases  of  parotid  fistula,  comes,  of 
course,  from  the  lining  membrane  of  the  ducts.* 

Upon  what  does  this  reaction  depend  ?  Shultz  supposed  it 
to  be  caused  by  ammonia.  This  is,  however,  impossible,  because 
the  fluid  distilled  from  saliva  is  not  alkaline,  because  saliva  eva- 
porated at  a  high  temperature,  is  increased  and  not  diminished 
in  alkalinity,  and  because  test-papers  discolored  by  it,  do  not 
regain  their  original  tint  when  heated.  These  phenomena  are 
incompatible  with  the  hypothesis  of  a  volatile  alkali.  Wright, 
Garrod,  and  others,  supposed  it  to  depend  on  free  soda,  mainly 
because  potassa  could  not  be  detected  in  it.  The  opinion,  first 
broached  we  believe  by  G.  Owen  Rees,  in  his  paper  on  Saliva, 
in  the  Cyclopcedia  of  Anatomy  and  Pliysiology,  that  the  tribasic 
phosphate  of  soda  is  the  cause  of  this  reaction,  appears  to  be 
gaining  ground.  Strength  is  given  to  it  by  the  generally  acknow- 
ledged fact  that  the  same  salt  communicates  alkalinity  to  serum. 

The  composition  of  parotid  saliva  does  not  differ  much  from 
that  of  the  common  fluid.  Like  the  latter,  it  contains  ptyalin, 
extractive  matter,  sulphocyanide  of  potassium,  epithelium,  and 
mucus  corpuscles,  a  volatile  acid  of  the  butyric  group  (probably 
caproic)  combined  with  potassa,  chlorides  of  sodium  and  potas- 
sium, a  small  amount  of  phosphates,  and  a  trace  of  alkaline  sul- 
phates. Lime  is  also  present,  sometimes  as  a  carbonate,  but 
oftenest  in  combination  with  organic  matter. 

The  saliva  of  the  submaxillary  gland,  according  to  Jacu- 
bowitsch  has  a  specific  gravity  of  1004.1,  a  less  strong  alkaline 
reaction,  and  less  combined  organic  matter  than  parotid  saliva. 

A  number  of  experiments  have  recently  been  made  at  Dorpat, 
by  Jacubowitsch,  under  the  direction  of  Bidder  and  Schmidt,  to 
determine  the  chemical  and  physiological  diff'erences  among  the 
diff'erent  salivary  secretions  of  dogs.  He  determined  the  consti- 
tution of 

*  Mitscherlich  found  that  it  required  .223  of  sulphuric  acid  to  neutralize 
100  of  parotid  saliva. 


SALIVA. 


165 


A.  Their  ordinary  or  mixed  saliva ; 

B.  Their  saliva,  excluding  the  parotid  secretion  ; 

C.  Their  saliva,  excluding  the  submaxillary  secretion; 

D.  Their  saliva,  excluding  the  parotid  and  submaxillary  se- 
cretions ; 

E.  Their  parotid  saliva  ;  and 

F.  Their  submaxillary  saliva. 

The  following  are  the  results  yielded  : — 

A.  B.  C.  D.         and        E. 


Water 
Solid  residue 


,;,^Epitbelium 

.^  Soluble  organic  matter 
Phosphate  of  soda 
>- Chloride  of  potassium 
^^  Chloride  of  sodium 
Sulphocjanide  of   po 
tassium  . 
^Phosphate  of  lime 
Phosphate  of  magnesia 
Carbonate  of  lime 


989.63 
10.37 


990.48 
9.52» 


)88.1 
11.9 


996.04 
3.96 


991.45       995.3 
8.55  4.7 


1000.00     1000.00     1000.0     1000.00     1000.00     1000.0 
2.24  I 


3.58 

0.82"] 

I 

5.82  \ 

J 
0.15 
10.37 


4.25 

4.08 

1.19 
9.52 


{.: 


04; 

4.20 


0.42 
11.90 


1.51 


2.89 


—  4.501 


1.4 


2.1 


-J     - 


1.16  — 
1.2 


1.51 


I 


All  these  different  secretions  coincide  in  being  unaffected 
by  nitric,  hydrochloric,  sulphuric,  phosphoric,  and  acetic 
acids,  and  by  solutions  of  ammonia  and  alum;  in  being  only 
rendered  slightly  turbid  by  ferrocyanide  of  potassium,  after 
previous  acidulation  with  acetic  acid,  and,  finally,  in  being  very 
strongly  precipitated  by  alcohol,  tannin,  and  acetate  of  lead. 
They  differ  in  the  following  particulars.  Parotid  saliva  exposed 
to  the  air,  becomes  rapidly  covered  with  a  film  of  crystals  of 
carbonate  of  lime,  which  is  not  the  case  with  either  of  the  other 
secretions.  At  the  temperature  of  boiling  water,  parotid  saliva 
does  not  become  turbid,  while  the  other  secretions  always  are 
rendered  at  least  slightly  opaque.  Boiled  with  nitric  acid 
and  then  treated  with  ammonia,  it  does  not  assume  the  yellow 
or  orange  tint  which  is  developed,  under  similar  circumstances, 


166  THE  CHEMISTRY  OF  THE  MOUTH. 

by  the  secretions  of  the  buccal  mucous  membrane  and  the  sub- 
maxillary glands ;  and  farthermore,  it  is  only  in  parotid  saliva 
that  carbonate  of  potash  produces  a  slight  precipitate  of  car- 
bonate of  lime. 

"We  return  now  to  the  chemistry  of  the  common  saliva,  -^-hich 
has  been  oftener  and  more  thoroughly  studied  than  that  from 
the  separate  glands.  One  of  the  most  characteristic  of  its 
organic  constituents,  and  one  of  the  most  important  to  the  due 
physiological  action  of  this  fluid  is  that  kno^Yn  as  ptyalin.  Un- 
fortunately, however,  the  greatest  confusion  prevails  among 
chemists  in  their  statements  of  the  nature,  composition,  and  re- 
actions of  this  substance.  Upon  a  careful  examination  of  their 
modes  of  obtaining  it,  it  becomes  manifest  that  they  have  been 
dealing  with  different  substances,  and,  consequently,  there  must 
be  discrepancies  in  their  accounts  of  the  physical  and  chemical 
characters  of  ptyalin.  This  will  be  plain  from  a  short  review  of 
the  various  deseriptions  they  have  left  us  of  their  manipulations 
and  experiments. 
/{j  Berzelius  first  separated  from  saliva  a  substance  to  which  he 
I  gave  the  name  of  salivary  matter  or  ptyalin.  He  first  evapo- 
rated the  saliva  to  dryness,  and  then  exhausted  it  with  alcohol, 
thus  removing  the  osmazome,  fat,  chlorides,  and  lactates.  The' 
solid  residue  being  alkaline,  was  neutralized  with  acetic  acid, 
and  the  acetate  removed  by  fresh  alcohol.  AVhat  remained, 
being  dried,  was  exhausted  by  water,  which  took  up  this  ptyalin, 
and  left  behind  mucus  with  earthy  sulphates  and  phosphates. 
"The  solution  of  this  matter  in  water,"  says  Berzelius,  -'is  a 
little  consistent,  and  is  not  troubled  by  ebullition.  After  eva- 
poration, the  salivary  matter  remains  colorless  and  transparent. 
If  water  is  then  poured  upon  this  last,  it  becomes  at  first  white, 
opaque,  and  mucous,  and  then  dissolves,  making  a  clear  solution, 
which  is  not  precipitated  by  tincture  of  galls,  chloride  of  mer- 
cury, subacetate  of  lead  nor  the  strong  acids,  characters  which 
distinguish  this  substance  from  a  great  number  of  other  animal 
matters." 

Dr.  Golding  Bird,  in  reviewing  the  characteristics  of  ptyalin, 
as  described  by  previous  chemists,*  comes  to  the  conclusion  that 

*  London  Med.  Gazette,  1840.    V 


SALIVA.  167. 

it  does  not  exist  as  a  distinct  principle.  His  reasons  for  this 
are,  first,  the  discrepancy  in  the  accounts  given  of  the  substance 
by  different  observers  ;  secondly,  the  constant  formation  of  new 
insoluble  matter  every  time  the  solution  is  evaporated,  a  point 
noticed  by  Gmelin,  Mitscherlich,  and  Schultz.  This  character 
certainly  approximates  this  substance  to  the  albuminate  of  soda. 
Dr.  Bird's  own  experiments  exhibit  still  farther  this  analogy. 
He  prepared  some  ptyalin,  according  to  the  process  of  Berzelius, 
and  then  exposed  it  to  the  action  of  a  courorme  de  tasses  of 
thirty-six  pairs.  "  Coagulation  ensued  at  both  electrodes,  but 
most  copiously  at  the  negative,  where  an  odor  of  chlorine  was 
evolved;  and  by  no  character  whatever  could  it  be  distinguished 
from  albumen." 

Simon's  method  of  obtaining  this  substance  is  analogous,  but 
not  entirely  similar  to  Berzelius's.  A  known  weight  of  saliva 
was  evaporated  to  dryness ;  the  loss  of  weight  thus  indicated 
the  proportion  of  water.  The  residue  was  treated  with  ether, 
which  extracted  the  fats.  The  solid  mass  remaining  was  next 
treated  with  water,  which  dissolved  out  the  ptyalin,  extractive 
matter,  and  salts,  leaving  behind  mucus,  albumen,  and  cells. 
Evaporated  to  a  small  bulk,  the  fluid  gives  up  its  ptyalin  as  a 
precipitate  on  the  addition  of  alcohol.  This  method  alone  is  a 
sufficient  refutation  of  Dr.  Bird's  hypothesis,  the  heat  used  in 
the  process  being  high  enough  to  coagulate  all  the  albumen  con-  ^  I 
tained  in  the  saliva.  O' 

Lehmann  says  that  it  is  obtained  in  greatest  purity  from  the 
spirit-extract  of  saliva,  after  repeated  extraction  with  alcohol 
and  ether.  It  is  combined  with  potash,  soda,  and  lime,  which 
may  be  separated  from  it  by  carbonic  or  some  stronger  acid, 
after  which  it  dissolves,  though  with  difficulty,  in  water.  When 
separated  by  the  acids,  it  falls  in  amorphous  flocculi,  which,  as 
already  said,  are  difficult  of  solution  in  pure  water,  but  dissolve 
readily  in  water  to  which  either  an  alkali  or  an  acid  has  been 
added. 

Its  reactions,  as  stated  by  the  latter  chemist,  sufficiently  dis- 
tinguish it  from  albumen,  while  they  show  it  to  be  intimately 
related  to  that  substance.  Acetic  acid,  added  to  its  alkaline 
solution,  throws  down  a  flocculent  precipitate  which  readily  dis- 


168  THE  CHEMISTRY  OF  THE  MOUTH. 

solves  in  an  excess  of  the  precipitate.  Boiled  with  Moride  of 
ammonium  or  sulphate  of  magnesia,  the  alkaline  solution  of 
ptyalin  becomes  very  turbid.  The  alkaline  solution  is  precipi- 
tated by  tannic  acid,  chloride  of  mercury,  and  basic  acetate  of 
lead,  but  not  by  alum,  sulphate  of  copper,  kc.  The  acetic  acid 
solutionis  strongly  precipitated  hj ferrocyanide  of  potassium, 
and  when  boiled  with  nitric  acid,  it  yields  a  yellow  color.  The 
resemblance,  it  will  be  observed,  is  much  more  striking  between 
this  substance  and  albuminose,  or  the  modified  albumen  of 
Mialhe,  than  between  it  and  normal  albumen.  Both  these  sub- 
stances, it  may  be  remarked,  are  albumen,  in  a  state  of  change, 
entering  the  economy.  The  physiological  analogies  between 
ptyalin  and  the  other  digestive  ferments  will  presently  be  alluded 
to.  When  these  are  all  considered,  it  would  appear  as  if  this 
were  the  result  of  the  waste  of  some  of  the  tissues  of  the  glands, 
probably  of  the  mucous  membrane  of  the  ducts  and  their 
ramifications,  still  undergoing  the  process  of  metamorphosis, 
and  therefore  acting  as  a  ferment. 

The  j^tytdin*  of  Dr.  Wright  must  not  be  confounded  with  the 
substance  we  have  just  described.  The  most  cursory  exami- 
nation of  his  experiments  suflSces  to  convince  us  of  its  distinct- 
ness. 

The  following  are  the  means  employed  by  him  for  preparing 
a  pure  specimen  of  ptyalin:  "First,  to  pass  saliva  through  ordi- 
nary filtering  paper,  and,  after  filtration  shall  have  been  com- 
pleted ;  secondly,  to  exhaust  the  residue  with  sulfuric  ether  : 
the  ethereal  solution  contains  a  fatty  acid  and  ptyalin.  It  is  to 
be  allowed  to  evaporate  spontaneously;  and,  thirdly,  the  residue 
left  by  evaporation  is  to  be  placed  upon  a  filter,  and  acted  upon 
by^istilled  Avater,  which  dissolves  the  ptyalin  and  leaves  the 
fatty  acid.  If  flie  aqueous  solution  be  carefully  evaporated  to 
dryness,  the  '  salivary  matter'  will  be  obtained  in  a  pure  state. 
Ptyalin,  as  thus  prepared,  is  a  yellowish-white,  adhesive,  and 
nearly  solid  matter,  neither  acid  nor  alkaline,  readily  soluble  in 
ether,  alcohol,  and  essential  oils,  and  more  sparingly  soluble  in 

*  Hereafter,  when  this  substance  is  alluded  to,  it  will  be  printed  in 
italics,  to  distinguish  it  from  the  ptyalin  of  other  authors. 


SALIVA.  169 

water.  It  alone  possesses  the  characteristic  odor  of  saliva ;  it 
is  unaffected  by  galvanism  and  most  of  the  agents  which  coagu- 
late albumen  ;  it  is  abundantly  precipitated  by  subacetate  of 
lead  and  nitrate  of  silver  ;  feebly  so  by  acetate  and  nitrate  of 
lead  and  tincture  of  galls,  uninfluenced  by  bichloride  of  mercury 
and  strong  acids  ;  the  latter  considerably  heighten  its  proper 
odor  and  impair  its  solubility,  whilst  alkalies  render  it  more 
soluble,  and  give  it  the  smell  of  mucus.  Moderate  heat  and 
oxygen  gas  also  increase  its  odor ;  but  intense  heat  or  cold 
diminishes  or  entirely  destroys  it.  At  a  suitable  temperature, 
ptyalin  may  be  preserved  for  any  length  of  time  without  risk  of 
decomposition.  The  salivary  fluid  from  which  ptyalin  has  been 
removed  by  filtration,  possesses  a  sickly  mucous  smell,  decom- 
poses much  sooner  than  ordinary  saliva,  and  in  the  process  of 
decay  invariably  evolves  ammonia.  If  this  fluid  be  heated,  the 
mucous  smell  will  be  increased  until  the  evaporation  shall  have 
been  continued  nearly  to  dryness,  when  a  slight  salivary  odor 
may  be  recognized,  due  to  a  portion  of  ptyalin  being  liberated 
from  the  mucus  with  which  it  was  previously  in  combination." 

The  other  constituents  of  saliva  are — extractive  matter,  soluble 
in  alcohol  and  water,  precipitable  bj  tannic  acid,  but  not  by 
alum  ;  sulphocyanide  of  potassium  ;  caproate  of  potassa  ;*  epi- 
thelium and  mucous  corpuscles  ;  chlorides  of  sodium,  potassium, 
and  calcium  ;  a  small  amount  of  phosphates  ;  traces  of  sulphates, 
lactates,  and  carbonates.  Lehmann  says  that  the  quantity  of 
the  latter  salts  in  the  fresh  secretion  must  be  extremely  small, 
and  that  the  alkaline  carbonates,  which  have  been  observed,  are 
formed  during  the  process  of  analysis  from  the  action  of  the 
atmospheric  air.  The  formation  of  carbonate  of  lime,  in  this 
manner,  in  the  parotid  secretion  of  the  horse,  may  be  easily 
seen — very  beautiful  crystals  of  this  salt  being  formed. 

In  the  parotid  saliva  of  the  dog,  the  solid  residue,  according 
to  Jacubowitsch,  amounts  to  0.47  per  cent.,  in  which  the  organic 
matter  is  to  the  inorganic  as  29.8 :  70.2;  the  latter  consisting 
of  44.7  of  alkaline  chlorides,  and  25.5  of  carbonate  of  lime.    In 

*  Probably.  It  is,  according  to  Lehmann,  the  potash-salt  of  a  not  very 
volatile  acid  of  the  butyric  acid  group.  The  crystals  under  the  microscope 
resembled  tufts  of  margaric  acid. 


<^ 


170  THE  CHEMISTRY  OF  THE  MOUTH. 

the  corresponding  fluid  of  the  horse,  Lehmann  found,  as  the 
mean  of  six  analyses,  0.708  per  cent,  of  solid  residue,  in  which 
the  organic  was  to  the  inorganic  matter  as  46.1  :  53.9.  The 
mean  amount  of  ptyalin  was  0.140  in  Lehmann's  experiments. 

The  presence  of  sulphocyanogen,  in  the  saliva,  was  for  a  long 
time  a  subject  of  quite  earnest  discussion.  At  last,  the  question 
is  settled  in  favor  of  those  who  believe  it  to  be  a  constant  ingre- 
dient in  this  secretion.  Whatever  may  be  its  physiological 
value,  it  is  a  matter  of  great  importance  in  a  medico-legal  point 
of  view,  to  determine  whether  it  is  a  normal  constituent  of  saliva  ; 
for,  in  a  state  of  sufficient  concentration,  it  strikes  with  the 
^        sesj^uichloride  of  iron  the  same  blood-red  tint  as  meconic  acid. 

Trevaranus  was  the  first  to  call  attention  to  this  reaction.  It 
is  unnecessary  to  go  into  the  history  of  the  discussion  upon  this 
point,  since  the  question  has  been  already  settled.  It  will 
suffice  to  mention  the  various  modes  of  proving  the- presence  of 
sulphocyanogen.  Dr.  Golding  Bird's  plan  is  to  acidulate  the 
0  saliva  with  nitric  afiid,  mingled  with  chloride__of  bai'ium,  and 
then  to  filter.  "No  change  will  occur  till  the  mixture  be 
warmed,  when  si^fimric  acid  will  be  formed  at  the  expense  of 
the  sulphocyanogen,  amT  a  copious  precipitate  of  sulphate  of 
barytes  will  be  formed."  Dr.  Percy  advises  that  the  residue  of 
carefully  dried  saliva  be  exhausted  with^  alcohol,  and  the  solu- 
tion be  subjected,  in  a  test-tube,  to  the  action  of  nascent  hydro- 
gen, which,  at  the  moment  of  its  escape,  decomposes  the  sul- 
phocyanogen, generating  sulphuretted  hydrogen,  which  may  be 
recognized  by  its  smell  and  its  action  upon  lead  paper.  A  piece 
of  pure  zinc,  with  sulphuric  acid,  is  a  convenient  substance  for 
generating  the  hydrogen.  Still  farther,  the  red  precipitate  with 
^"^  the  p^ers^dtof  iron  may  be  easily  tested.  If  it  is  a  sulpho- 
cyanide,  lieaTwiTI  temporarily  destroy  its  color ;  a  reaction  which 
distinguishes  it  equally  from  the  meconates,  formates,  and  ace- 
tates. Another  simple  and  easy  method  of  recognizing  the  pre- 
cipitate from  a  solution  containing  sulphocyanogen,  is  to  drop  a 
crystal  of  corrosive  sublimate  in  the  red  fluid.  If  the  tint  be 
produced  by  sulphocyanide,  the  color  vanishes  ;  if  by  any  of  the 
acids  alluded  to,  it  is  unchanged. 

There  are  two  modes  in  which  the  quantitative  determination 


SALIVA.  171 

of  this  substance  may  be  made.  The  alcoholic  extract  ma}^  be 
dissolved  in  water ;  the  solution  filtered  to  free  it  from  fat ;  the 
filtrate  concentrated,  treated  with  sulphuric  acid  and  distilled. 
The  distillate  must  then  be  saturated  with  Jjarytg^and  filtered, 
and  the  filtered  fluid  evaporated.  The  residue  is  to  be  boiled 
with  fuming  nitric  acid  or  aqua  regia,  and  the  amount  of  sul- 
phocyanogen  calculated  from  the  sulphate  of  baryta,  which  sepa- 
rates. The  other  method  is,  to  precipitate  the  same  aqueous  . 
solution  with  niti'ate  ofsilyer,  to  wash  the  precipitate  well,  to 
treat  it  with  water  containing  nitric  acid,  which  does  not  dissolve 
the  chloride  of  silver ;  the  silver  is  precipitated  from  the  acid 
solution  by  hydrochloric  acid,  a  little  chlimde__of  barium  is  '^ 
added,  the  solutioirTs~~evaporated,  a  little  nitric  acid  being  re- 
peatedly added.  We  thus,  also,  obtain  sulphate  of  baryta,  from 
which  the  sulphocyanogen  is  to  be  calculated.  It  must  be  borne 
in  mind,  however,  in  all  calculations  of  this  kind,  that,  according 
to  Dr.  "Wright,  this  ingredient  of  the  saliva  is  temporarily  aug- 
mented by  any  local  stimulation  of  the  glands,  by  the  internal 
use  of  prussic  acid,  the  cyanides,  and  sulphur,  especially  by  the 
last-named  substance. 

Kletzinsky*  has  recently  investigated  this  subject.  He  tested 
the  saliva  by  letting  it  drop  from  the  mouth  into  a  small  white 
porcelain  basin,  and  then  added,  drop  by  drop,  a  normal  solution 
of  neutral  sesquichloride  of  iron  (1  part  of  FcaClj  to  10  of  water),  * 

stirring  the  mixture  with  a  glass  rod,  till  the  maximum  degree 
of  redress  was  obtained.     The  following  are  his  results  : — ■ 

1.  Taking  the  morning  reaction  as  the  normal  type,  the  sul- 
phocyanogen is  most  abundant  after  meals,  and  most  deficient 
in  the  evening. 

2.  On  fasting,  it  diminishes  most  rapidly  towards  evening, 
and  hardly  attains  its  average  quantity  in  the  morning. 

3.  Its  quantity  is  diminished  by  alcoholic  drinks,  and  is  in- 
creased by  coffee,  pepper,  salt,  and  spices ;  still  more  so  by 
mustard,  garlic,  and  radishes. 

4.  Peruvian  balsam  always  causes  an  augmentation ;  and 
musk,  in  half-grain  doses,  produces  a  very  great  increase. 

*  Quoted  by  Dr.  Day,  in  the  British  and  Foreign  Medico-CIiirurgical 
Review  fur  July,  1853. 


172  THE  CHEMISTRY  OF  THE  MOUTH. 

5.  The  use  of  iodine  diminishes  it. 

6.  In  true  ptyalorrhoea,  the  sulphocyanogen  is  always  very 
much  diminished,  or  actually  disappears  ;  but  hydrosulphate  of 
ammonia  is  present  as  a  product  of  its  decomposition. 

7.  In  almost  all  chronic  exhausting  diseases,  the  sulphocy- 
anogen is  diminished,  while,  during  convalescence,  it  is  usually 
a  little  above  the  average. 

8.  It  is  relatively  deficient  in  infancy  and  old  age,  and  in  the 
latter  months  of  pregnancy. 

9.  In  all  conditions  of  excitement,  whether  psychical  or 
somatic,  it  is  always  somewhat  increased,  till  depression  begins 
to  supervene.  It  was  very  much  augmented  in  a  male  lunatic 
addicted  to  onanism,  and  in  an  insane  woman  with  nymphomania. 

"  The  only  conclusion,"  says  Dr.  Day,  "  at  which  we  can  at 
present  arrive  is,  that  the  quantity  of  sulphocyanogen  may,  in 
some  measure,  be  regarded  as  proportional  to  the  intensity  of 
the  vital  processes." 

After  dilution  with  water,  saliva  lets  fall  a  flaky  precipitate, 
which  is  dissolved  by  boiling,  and  deposited  again  on  cooling. 
Saliva  freezes  at  a  lower  temperature  than  water.  Wright  says 
he  has  never  seen  the  healthy  liquid  resist  10°  F.,  though  in 
disease  it  may  remain  fluid  at  0°. 

Saliva  has  a  strong  affinity  for  oxygen,  absorbs  it  readily 
from  the  air,  and  imparts  it  to  other  bodies.  It  has  been  even 
said  to  oxidate  gold  and  silver,  when,  in  minute  division,  they 
are  triturated  with  it.  The  latter  metal  is  undoubtedly  affected 
by  it.  In  manufacturing  mercurial  ointment,  it  has  long  been 
known  that  the  globules  are  broken  down  more  readily  when 
the  operator  spits  in  the  mortar,  and  the  oxidizable  metals  are 
always  more  corroded  by  this  fluid  than  by  pure  water.  Pure 
saliva,  according  to  Wright,  absorbs,  on  an  average,  its  own 
volume  of  oxygen,  though  this  is  liable  to  variation,  from  two 
and  a  quarter  times  to  one-half  the  bulk  of  the  secretion.  This 
diff"erence  is  supposed  to  be  due  to  the  carbonic  acid  gas  con- 
tained in  the  secretion,  which  varies  from  one-eighth  to  one- 
twelfth  in  volume,  though  it  is  sometimes  more  abundant.  This 
gas  is  absorbed  in  the  same  ratio,  but  hydrogen  and  nitrogen  in 
less  proportion. 


SALIVA.  .  173 

Exposed  to  the  air  at  a  temperature  of  60°  F.,  saliva  readily 
putrefies.  Decomposition  commences  at  from  the  third  to  the 
seventh  day,  the  ptyalin  generally  being  the  first  ingredient  to 
suffer.  "  Ammonia  is  usually  formed  during  the  process  of 
decay ;  but,  if  the  saliva  have  been  previously  heated  to  212° 
F.,  it  decomposes  very  slowly,  and  the  product  of  destruction  is 
generally  an  acid.  The  addition  of  an  acid  to  saliva  also  assists 
in  its  preservation  ;  whilst  caustic  alkali,  which  almost  immedi- 
ately causes  the  evolution  of  ammonia,  promotes  rapid  decom- 
position. If  saliva  be  carefully  evaporated  to  dryness,  it  will 
retain  its  odor  and  properties  in  an  unimpaired  state  for  many 
months."* 

The  destructive  distillation  of  this  secretion  produces,  ac- 
cording to  the  same  accurate  observer  we  have  so  often  quoted, 
carbonate  of  ammonia,  oily  matter,  acetic  and  lactic  acids,  but 
never  the  hydrocyanic.  The  residue  consists  chiefly  of  phos- 
phates and  chlorides,  with  a  little  carbonate. 

The  analysis  of  saliva  has  been  conducted  in  different  ways 
by  different  chemists.     "Wright's  method  was  as  follows: — 

"  The  saliva  is  to  be  filtered  through  moderately  coarse  filter- 
ing-paper. On  the  filter  will  remain  a  solid  residuum  (1),  and 
a  clear  liquid  (2)  will  have  passed  through. 

^^Examination  of  Solid  Residuum  (1). — It  is  to  be  washed 
thoroughly  on  the  filter  with  ether,  when  a  residue  (A)  will  be 
left,  and  an  ethereal  solution  (B)  will  be  obtained.  '^ 

^'"Examination  of  (A). — Exhaust  with  cold  distilled  water; 
this  dissolves  the  chlorides  of  sodium  and  potassium  (a,  5),  which 
may  be  obtained  by  evaporation.  The  matter  left  upon  the 
filter  is  to  be  dried,  weighed,  and  then  incinerated.  The  amount 
of  loss  thus  occasioned  indicates  the  proportion  of  free  albumen 
(c).  A  little  ash  remains,  from  which  distilled  water  extracts 
carbonate  of  soda  (tZ),  and  leaves  phosphate  of  lime  [e).         . 

'•'■Examination  of  (B). — Evaporate  carefully  to  dryness. 
"Wash  the  residuum  on  a  filter  with  distilled  water,  and  continue 
to  treat  with  this  menstruum  until  everything  soluble  in  it  is 
removed.     The  aqueous  solution  is  next  to   be  evaporated  to 

*  Wright,  op.  clt. 


174  THE  CHEMISTRY  OF  THE  MOUTH. 

dryness,  when  a  residue  of  pure  ptyalin  (/)  will  be  obtained. 
The  matter  left  upon  the  filter  is  a  fatty  acid  (^),  which  is  to  be 
dissolved  in  sulphuric  ether,  from  which,  by  evaporation,  it  may 
be  obtained  in  a  pure  form. 

'■^Examination  of  Filtered  Liquid  [2). — This  liquid  is  affected 
neither  by  boiling  nor  by  nitric  acid  ;  yet  it  contains  albuminate 
of  soda  (7t),  which  can  only  be  separated  by  means  of  galvanism. 
To  this  end,  it  is  advisable  to  reduce  the  liquid  by  very  careful 
evaporation,  one-third  in  volume,  and  then  to  introduce  the 
wires  of  a  galvanic  battery  in  action  ;  free  soda  will  collect 
upon  the  negative  pole,  and  coagulated  albumen  upon  the  posi- 
tive one.  In  tliis  manner  all  the  albuminate  of  soda  may  be 
removed  without  decomposing  the  chlorides. 

"The  liquid  having  been  thus  treated,  is  next  to  be  very  care- 
fully evaporated  to  dryness,  and  the  dry  residuum  exhausted 
with  ether,  which  dissolves  the  lactates  of  potassa  and  soda 
(z,  y),  and  sulphocyanide  of  potassium  [k).  These  salts,  having 
been  dried  and  weighed,  are  to  be  dissolved  in  distilled  water, 
and  subacetate  of  lead  is  to  be  added  to  the  solution  until  it 
shall  cease  to  afford  a  precipitate.  An  insoluble  sulphocyanide 
of  lead  will  be  deposited,  and  a  soluble  lactate  will  remain  in 
solution.  The  former,  after  having  been  dried  and  weighed, 
will  indicate  the  proportion  of  sulphocyanide  of  potassium  pre- 
viously existing  in  the  saliva ;  and  by  subtracting  this  weight 
from  that  of  the  original  saline  matter,  the  quantity  of  lactates 
will  also  be  determined. 

"  The  residuum  from  which  these  salts  have  been  separated 
is  to  be  treated  with  alcohol,  which  Avill  remove  the  remaining 
chlorides  of  sodium  and  potassium,  the  weight  of  which  is  to  be 
added  to  that  of  (a,  h). 

"After  the  extraction  of  the  chlorides,  the  soda  which  remains 
in  the  form  of  carbonate,  is  to  be  neutralized  by  acetic  acid, 
and  the  salt  dissolved  out  by  alcohol ;  by  evaporating  the  alco- 
holic solution  to  dryness,  and  exposing  the  salt  to  a  red  heat, 
the  acetic  acid  will  be  destroyed,  and  the  soda  [T)  left. 

"The  remaining  solid  matter  is  to  be  dried,  weighed,  and  in- 
cinerated. The  loss  by  incineration  determines  the  amount  of 
mucus  {m). 

"  The  saline  matter  left,  is  to  be  boiled  in  distilled  water, 


SALIVA.  175 

■which  will  generally  remove  a  little  sulphate  or  phosphate  of 
potass  or  soda — usually  a  phosphate  of  soda  (w). 

"The  last  residuum  will  be  a  phosphate  of  lime;  its  weight 
must  be  added  to  that  of  (e). 

"Silica  is  mentioned  as  a  constituent  of  saliva.  I  have  never 
met  with  it,  though  I  have  occasionally  discovered  a  trace  of 
iron." 

Simon's  plan  differs  somewhat  from  this.  He  evaporated  a 
known  quantity  to  dryness,  and  thus  determined  the  water.  He 
then  treated  the  residue  with  ether  to  extract  the  fats;  and  with 
water  to  take  up  the  ptyalin,  extractive,  and  salts.  "  The  in- 
soluble residue  that  had  resisted  the  action  of  ether  and  Avater, 
consisted  of  albumen  and  mucus.  Another  portion  of  the  saliva 
was  decanted  from  its  precipitate,  evaporated  to  a  small  residue, 
and  the  ptyalin,  with  a  trace  of  extractive  matter,  precipitated 
by  alcohol.  When  the  saliva  contains  a  caseous  matter  (which 
I  have  observed  in  large  quantity  in  the  saliva  of  the  horse),  the 
precipitate  of  ptyalin  and  casein  produced  by  the  alcohol,  must 
be  dissolved  in  water,  and  the  casein  then  thrown  down  by  the 
careful  addition  of  acetic  acid.  In  this  case,  a  portion  of  the 
casein  precipitated  by  the  alcohol  usually  remains  undissolved  by 
the  water.  I  have  detected  free  acetic  acid  in  the  saliva,  dis- 
charged during  salivation.  In  order  to  determine  its  quantity, 
the  saliva  must  be  accurately  neutralized  by  a  solution  of  car- 
bonate of  potash  of  known  strength  ;  from  the  amount  of  the 
alkaline  solution  required,  the  quantity  of  acetic  acid  can  be 
calculated.  If,  in  addition  to  acetic  acid,  free  lactic  acid  is 
likewise  present,  the  residue  of  the  saliva,  after  evaporation, 
when  dissolved  in  water,  will  still  indicate  an  acid  reaction,  be- 
cause lactic  acid  differs  from  acetic  acid  in  not  being  volatilized 
at  the  ordinary  temperature  used  for  evaporating  animal  fluids. 
In  order  to  determine  the  amount  of  free  soda  in  the  saliva,  the 
dried  residue  must  be  extracted  with  alcohol,  the  free  soda 
(which  is  left  in  the  residue)  must  be  saturated  with  acetic  acid, 
the  resulting  acetate  of  soda  extracted  with  alcohol,  evaporated, 
and  by  incineration  reduced  to  carbonate  of  soda."* 

Lehmann's  method  is  also  different  from  Wright's,  as  will  be 

*  Animal  Chemistry. 


176  THE  CHEMISTRY  OF  THE  MOUTH. 

seen  by  the  following  account,  "which  we  give  in  his  own  words, 
as  translated  by  Dr.  Day  : — 

"  In  the  first  place,  the  saliva  must  always  be  filtered,  in 
order  to  efi'ect  the  removal  of  the  epithelial  scales;  unfortunately, 
however,  the  saliva  is  often  so  viscid  and  tenacious,  that  it  under- 
goes decomposition  before  passing  through  the  filter  ;  indeed,  it 
generally  happens  that  the  small  quantity  of  filtered  and  per- 
fectly clear  fluid  begins  to  become  turbid,  while  the  greater  por- 
tion of  the  fluid  still  remains  upon  the  filter.  In  such  cases  it 
is  often  advisable  to  dilute  the  saliva  with  three  or  four  times 
its  volume  of  boiling  water;  and  after  the  mixture  has  been  as 
thoroughly  as  possible  cooled,  and  the  mucous  flocculi  for  the 
most  part  deposited,  to  filter  and  proceed  with  the  analysis;  but 
as  in  this  case  we  are  not  able  to  separate  the  soluble  from  the 
insoluble  portion,  it  is  best  not  to  attempt  the  whole  analysis, 
since  we  should  only  obtain  inaccurate  results.  We  might  cer- 
tainly at  once  evaporate  the  viscid  fluid,  in  order  to  extract  the 
residue  with  alcohol,  ether,  and  finally  with  water ;  but  inde- 
pendently of  the  circumstance  that  the  aqueous  extract  is  also 
difficult  of  filtration,  substances  would  be  taken  up  by  the  alco- 
hol and  ether,  which  do  not  pertain  intrinsically  to  the  saliva, 
but  to  the  epithelial  cells,  and  to  the  fat  and  remains  of  food 
sometimes  mixed  with  them. 

It  is  obvious  that,  if,  before  submitting  the  saliva  to  a  chemi- 
cal analysis,  we  duly  examine  its  morphological  elements  with 
the  microscope,  we  can  ascertain  whether  the  insoluble  parts  of 
the  saliva  consist  merely  of  epithelial  cells  and  mucous  corpus- 
cles, or  whether  they  also  contain  fat,  vibriones,  or  molecular 
granules  of  an  organic  nature.  In  saliva  which  has  been  for  a 
long  time  exposed  to  the  air,  in  morbid  saliva,  and  especially 
where  it  exhibits  an  acid  reaction,  such  granules  are  of  very 
frequent  occurrence.  As  substances  for  the  most  part  in  an 
actual  state  of  change,  they  do  not  fall  within  the  domain  of  an 
accurate  chemical  analysis.  No  one  can  confound  mineral  sub- 
stances, as,  for  instance,  crystals  of  carbonate  of  lime,  with 
these  molecular  granules. 

If  the  saliva  has  been  filtered,  no  interest  attaches  to  any  in- 
vestigation of  the  residue  left  on  the  filter,  at  least  in  so  far  as 


SALIVA.  177 

the  nature  of  the  saliva  is  concerned,  seeing  that  true  saliva 
contains  only  soluble  substances. 

Wright  finds  his  ptyalin  in  this  residue;  he  cannot,  however, 
possibly  have  treated  this  residue  with  sufficient  water,  since, 
in  that  case,  it  could  not  have  contained  so  large  a  quantity  of 
matter  soluble  in  water  as  his  numbers  indicate. 

If  carbonate  of  lime  be  mixed  with  this  residue  insoluble  in 
water,  it  may  be  easily  extracted  by  very  dilute  acetic  acid,  and 
its  quantity  subsequently  determined. 

In  reference  to  the  filtered  solution,  it  is  generally  of  interest 
to  determine  volumerically  the  amount  of  acid  which  is  saturated 
by  a  certain  quantity  of  saliva,  in  order  to  form  an  opinion  in 
regard  to  the  alkalinity  of  the  saliva,  or,  in  other  words,  regard- 
ing the  quantity  of  the  weakly-combined  alkali.  In  every  case, 
however,  the  filtered  saliva  must  be  neutralized  with  acetic  acid, 
and  then  heated;  if  this  gives  rise  to  a  turbidity,  the  albuminous 
substance  which  is  precipitated  must  be  collected  on  a  filter,  and 
determined  quantitatively.  The  residue  left  on  the  evaporation 
of  the  filtered  saliva  is  then  to  be  treated  in  the  same  manner  as 
we  treat  the  residue  in  the  case  of  most  of  the  other  animal 
fluids."* 

The  method  of  determining  the  sulphocyanogen,  we  have 
already  spoken  of. 

The  following  are  the  results  obtained  by  some  of  the  most 
distinguished  observers. 

Berzelius  found  in  1,000  parts  of  human  saliva — 
Water  ...       r         ...         .     992.9 


Ptyalin 

2.9 

Mucus .         .         .         .         . 

1.4 

Extract  of  flesh  with  alkaline  lactates    . 

.9 

Chloride  of  sodium        .         .         .  •       . 

1.7 

Soda    ....... 

.2 

*  Lehmann's  Physiological  Chemistry,  vol.  ii.  p.  22,  English  edition. 
12 


178 


THE  CHEMISTRY  OF  THE  MOUTH. 


The  result  obtained  by  Simon,  from  his  own  saliva,  was- 


Water 

991.225 

Solid  constituents — 

Fat,  containing  cholesterin 

.525 

Ptyalin,  with  extractive  matter   . 

4.375 

Extractive  matter  and  salts 

2.450 

Albumen,  mucus,  and  cells 

1.400 

8.775 

1,000. 
Wright's  analysis,  in  which,  it  mustbe  remembered,  the  ptyalin 
differs  from  that  of  Berzelius  and  Simon,  gave — 


Water 

988.1 

Ptyalin 

1.8 

Fatty  acid 

.5 

Chlorides  of  sodium  and  potassium 

1.4 

Albumen  with  soda 

.9 

Phosphate  of  lime 

.6 

Albuminate  of  soda 

.8 

Lactates  of  potash  and  soda  . 

.7 

Sulphocyanide  of  potassium  . 

.9 

Soda 

.5 

Mucus,  with  ptyalin      .         .         .         . 

2.6 

The  analysis  published  by  Frerichs,  and  co 

pied  \ 

)y  Carpenter, 

in  the  last  edition  of  his  Principles  of  Huma 

nPh 

fsiology^  from 

which  we  quote  it,  does  not  precisely  corresp 

ond  w 

ith  either  of 

the  others. 

Water     ....".. 

994.10 

Solid  matter — 

Ptyalin,  with  a  little  alcohol  extract    '. 

L.41 

Mucus  and  epithelium  .         .         .     i 

2.13 

Fatty  matter        .... 

.07 

Sulphocyanide  of  potassium  . 

.10 

Alkaline  and  earthy  chlorides  and  ^ 

phosphates        .         .         .        >     ^ 

2.19 

Oxide  of  iron     .  .        .        .J 

5.90 

1,000.00 


SALIVA.  179 

The  analysis  of  Jacubowitsch  is  given  below.  The  soluble  organic 
matter  mentioned  in  it  is  what  the  other  chemists  call  ptyalin. 


Water 

, 

995.16 

Solid  constituents — 

Epithelium  .... 

.     1.82 

Soluble  organic  matter 

.     1.34 

Sulphocyanide  of  potassium 

.     0.06 

Fixed  salts  .... 

.     1.82 

4.34 

Loss        .         . 

• 

0.50 

1,000.00 
In  regard  to  these  analyses,  Wright  says  he  made  about 
twenty  of  healthy  saliva,  and  that  no  two  of  them  exactly  cor- 
responded. The  variation  between  Frerichs  and  Wright,  is 
especially  manifest  in  the  estimation  of  the  sulphocyanide  of 
potassium.  Both  of  them  are  beyond  Jacubowitsch  and  Lehmann. 
The  first  of  these  chemists  found  0.06  parts  of  this  salt  in  a 
thousand  of  his  own  saliva,  and  the  second  states  its  variation 
at  0.046  to  0.089.  Frerichs's  advance  upon  the  last  is  but 
trifling. 

In  regard  to  the  elimination  of  substances  taken  into  the  sys- 
tem through  the  medium  of  this  secretion,  Lehmann  shows  that 
many  of  them  pass  off  more  rapidly  by  the  salivary  glands  than 
by  the  kidneys.  Thus,  iodide  of  potassium  being  taken  in  the 
form  of  pill,  iodine  may  be  detected  in  the  saliva  in  ten  minutes, 
while  it  requires  from  half  an  hour  to  two  hours  to  detect  the 
same  in  the  kidneys.  Bromine,  mercury,  and  other  sialagogues, 
obey  the  same  law.  Lehmann,  like  many  of  the  earlier  observers, 
found  mercury  in  the  saliva  discharged  during  mercurial  saliva- 
tion.    We  shall,  however,  return  to  this  theme  again. 

The  physiological  use  of  saliva  has  long  been  a  subject  of 
debate  among  the  learned,  and  it  is  doubtful  whether  it  can  yet 
be  regarded  as  fully  and  satisfactorily  ascertained.  Dr.  Wright, 
in  commencing  his  investigations  in  reference  to  this  particular, 
first  endeavored  to  ascertain  its  influence  upon  vegetable  and 
animal  life.  We  have  no  room  even  for  an  abstract  of  his 
extremely  interesting  experiments,  and  refer  our  readers  who 


180  THE  CHEMISTRY  OF  THE  MOUTH. 

desire  information  on  this  subject,  to  his  papers  in  the  Lancet 
for  1842,  and  to  the  British  and  Foreign  Medical  Review  for 
January,  1847.  Suffice  it  to  say,  that  vegetables  were  injuri- 
ously affected  by  it,  while  their  seeds  escaped,  and  that  animals 
were  destroyed  by  it  when  their  veins  were  injected  with  it. 
Dogs  manifested  unequivocal  signs  of  hydrophobia  in  several 
instances,  and  in  nearly  all  perished  with  symptoms  of  great  dis- 
turbance of  the  nervous  system,  Jacubowitsch  and  Lehmann 
both  deny  that  saliva  exerts  this  deleterious  influence  over  either 
plants  or  animals. 

Pringle's  experiments  are  not  to  be  neglected  by  the  student 
who  wishes  to  get  an  idea  of  the  influence  which  this  fluid  exerts 
over  the  digestive  processes.  He  beat  up,  in  a  mortar,  two 
drachms  of  fresh  meat,  the  same  quantity  of  bread,  with  an 
ounce  of  water,  and  so  much  saliva  as  he  thought  necessary  for 
digestion ;  put  the  mixture  in  a  closed  phial,  and  set  it  in  a  fur- 
nace. It  remained  two  days  without  any  visible  fermentation, 
but,  on  the  third,  the  bread  and  flesh  had  risen  in  the  water,  a 
sediment  was  forming,  and  bubbles  of  air  continually  escaping, 
this  action  being  accompanied  by  the  vinous  smell,  common  to 
fermenting  liquors.  When  completed,  the  fluid  had  a  pure  acid 
taste  without  any  putrid  smell,  from  which,  indeed,  it  had  been 
free  during  the  whole  time  of  the  experiment.  He  thought  that 
healthy  saliva  was  "  qualified  for  retarding  putrefaction,  pre- 
venting immoderate  fermentation,  acidity,  and  flatulence  in  the 
primx  vise.''  A  subsequent  experiment  with  putrid  saliva, 
showed  that  this  liquid  in  that  state  brought  on  fermentation 
sooner,  made  the  flesh  unusually  putrid,  but,  at  last,  in  conse- 
quence of  the  acid  generated,  removed  the  ofi"ensive  odor. 

Leuchs  is  usually  supposed  to  be  the  first  to  discover  that 
saliva  had  the  property  of  converting  starch  into  sugar,  but  Dr. 
Wright  has  expended  much  learned  research  to  show  that  this 
action  upon  starch  was  known  long  before  the  announcement  of 
that  chemist's  experiments  in  1831.  He  quotes  Boerhaave, 
Plenck,  Mundius,  and  a  host  of  others  to  show  that  the  influence 
of  saliva  in  producing  a  saccharine  fermentation  in  farinaceous 
liquids  was  well  known  to  the  older  writers.  The  favorite  drink 
of  the  American  savages,  according  to  the  statements  of  these 


SALIVA.  181 

authors,  was  formed  by  beating  up  maize,  cassava,  or  some  other 
amylaceous  substance  with  water,  into  which  were  thrown,  from 
time  to  time,  fragments  of  the  same  substance,  which,  having 
been  chewed  by  the  women,  were  thoroughly  saturated  with 
saliva,  and  so  acted  as  a  ferment,  inducing  the  desired  degree  of 
saccharine  change  in  the  mass.  Schwann  corroborated  Leuchs's 
statement  by  his  experiments.  He  found  that,  when  boiled 
starch  was  digested  for  twenty-four  hours  in  saliva,  it  no  longer 
gave  a  blue  tint  on  the  addition  of  iodine.  On  neutralizing, 
drying,  and  digesting  in  alcohol,  he  obtained  sugar,  recognized 
by  its  taste  and  its  property  of  fermenting  with  yeast.  The 
residue,  which  alcohol  did  not  dissolve,  was  found  to  be  salivary 
matter  and  starch  altered  to  a  substance  resembling  gum,  with 
which  iodine  did  not  produce  a  blue  tint. 

Wright  has  investigated  this  subject  with  his  usual  accuracy 
and  candor.  He  ascertained,  as  the  result  of  a  number  of  ex- 
periments, that  the  production  of  sugar  from  starch  is  a  con- 
stant result  of  the  action  of  saliva  upon  the  latter  substance. 
Fresh  saliva  seemed  to  have  the  most  powerful  action,  though 
this  catalytic  or  zymotic  power  remained  even  after  boiling. 
Hydrogen  and  nitrogen  seemed  to  diminish  the  activity  of  the 
saliva.  Oxygen  did  not  appear  to  increase  it.  The  addition 
of  either  acids  or  alkalies  prevented  the  development  of  sugar 
in  the  mixed  liquids. 

The  same  observer  was  satisfied  that  this  fluid  exerted  a  di- 
gestive influence  over  meats.  He  found  that,  on  subjecting  the 
same  meat  to  water  and  to  saliva  at  the  same  temperature,  fer- 
mentation went  on  rapidly  in  that  portion  immersed  in  the  saliva, 
while  in  that  digested  in  water  there  was  no  perceptible  change. 

The  most  conclusive  of  his  experiments,  however,  in  this  de- 
partment of  inquiry,  are  those  performed  on  two  dogs  of  about 
the  same  weight,  and  both  in  perfect  health.  Into  the  stomach 
of  one  of  these  animals,  after  a  fast  of  twenty  hours,  were 
injected  eight  ounces  of  lean,  raw  beef,  and  the  same  quantity  of 
bread,  beaten  to  a  pulp  with  ten  ounces  of  water.  The  gullet 
was  tied  and  the  saliva  tested,  and  found  to  be  alkaline.  "  In 
half  ayi  hour  its  strength  of  alkalinity  ivas  at  least  doubled  ;  the 
quantity  of  the  secretion  was  also  much  augmented.     The  alka- 


182  THE  CHEMISTRY  OF  THE  MOUTH. 

line  reaction  of  the  saliva  gradually  increased,  till,  at  the  end  of 
three  hours,  it  contained  3.14  |;er  cent,  of  alkali.''  The  animal 
being  killed  by  introduction  of  air  into  the  jugular  vein,  the  food 
was  found  unaltered,  except  by  the  addition  of  mucus,  and  the 
contents  of  the  stomach  had  a  sour  smell.  That  viscus  was  deeply 
reddened,  the  tint  being  three  or  four  times  deeper  than  is  cus- 
tomary during  digestion.  On  the  second  dog  the  same  experi- 
ment was  performed,  differing  only  in  the  substitution  of  ten 
ounces  of  alkaline  saliva  for  the  ten  ounces  of  water  in  the  pre- 
ceding experiment.  The  saliva  here,  too,  at  the  beginning,  was 
moderately  alkaline.  '"''At  the  end  of  half  an  hour  the  secretion 
ivas  scarcely  altered,  either  in  character  or  quantity.  When  two 
hours  had  elapsed  the  mouth  was  very  frothy,  but  the  saliva  was 
little  changed.  At  the  end  of  three  hours  the  mouth  was  still 
frothy,  and  the  saliva  contained  only  .h9  j!?er  cent,  of  alkali. 
The  animal  being  killed  in  the  same  way,  the  contents  of  the 
stomach  were  found  not  particularly  acid,  nor  its  mucous  mem- 
brane more  vascular  than  in  healthy  digestion.  The  food  was 
reduced  to  a  perfectly  homogeneous  pulp. 

Dr.  Wright's  conclusions  from  his  experiments  are : — 
"  1.  Saliva  has  the  power  of  modifying,  and,  to  a  certain  extent, 
of  digesting  vegetable  and  animal  substances. 

"  2.  It  has  a  more  powerful  action  upon  vegetable  than  upon 
animal  matters. 

"  3.  The  healthy  digestive  action  of  saliva  is  always  attended 
with  the  evolution  of  lactic  acid. 

"  4.  Filtration,  or  boiling,  diminishes  the  digestive  powers  of 
saliva,  but  does  not  destroy  them. 

"  5.  Exposure  of  the  saliva  to  atmospheric  air  for  a  moderate 
length  of  time,  does  not  materially  weaken  its  digestive  powers, 
but  they  are  enfeebled  in  the  ratio  of  the  putrescency  of  the 
secretion. 

"  6.  Oxygen  gas  assists  the  digestive  action  of  saliva,  but  is  not 
essential  to  it.  Carbonic  acid  gas  impairs  this  action  in  a  mild 
degree,  and  hydrogen  and  nitrogen  gases  weaken  it  very  con- 
siderably. 

"7.  Acids  or  alkalies  added  to  saliva,  diminish  or  destroy  its 
digestive  properties. 


SALIVA.  183 

"  8.  The  presence  of  saliva  in  the  stomach  is  essential  to  healthy 
digestion. 

"9.  The  digestive  action  of  saliva  is  not  possessed,  in  any  effi- 
cient degree,  by  animal  mucus,  acids,  alkalies,  or  alkaline  salts." 

According  to  the  same  authority,  all  stimulation  of  the  sto- 
mach by  alcohol,  spices,  or  acescent  food,  is  accompanied  by  a 
marked  increase  in  the  alkalinity  of  the  saliva.  "When  spitting 
much  after  a  full  meal,  he  never  failed  to  have  acidity  and  pain 
of  the  stomach,  with  corresponding  alkalinity  of  the  saliva.  A 
dose  of  carbonate  of  soda,  neutralizing  the  gastric  acidity, 
irouglit  down  the  saliva  to  its  usual  standard  of  feeble  alkalinity 
in  a  few  minutes,  and  often  in  a  few  seconds.  Acids  introduced 
into  the  stomach,  raw  turnips,  onions,  and  other  indigestible 
substances,  produced  the  same  effect  upon  the  saliva.  The  im- 
portance of  this  fluid  in  digestion  is  farther  shown  by  the  dys- 
pepsia consequent  upon  its  waste.  This  is  undoubtedly  one  of 
the  sources  of  that  ill-health  with  which  inveterate  chewers  and 
smokers  are  sometimes  afilicted.  "Frequent  attacks  of  dys- 
pepsia, to  which  I  was  once  happily  a  stranger,"  says  "Wright, 
"  painfully  remind  me  of  the  injury  I  sustained  in  the  course  of 
my  investigations.  I  once  spat  two  hundred  and  fifty  drachms 
of  saliva  in  one  week,  and  from  the  nature  of  my  experiments,  I 
was  often  compelled  to  spit  directly  after  dinner  ;  in  that  seven 
days  I  lost  eleven  pounds  in  weight,  and  was  much  weakened 
and  emaciated." 

The  uses  of  this  fluid  in  the  economy  are  divided,  by  the 
author  just  quoted,  into  active  and  passive  ;  the  active  being,  (1) 
stimulation  of  the  stomach,  (2)  aiding  digestion  by  a  specific 
action  upon  the  food,  (3)  neutralization  of  undue  acidity  by  sup- 
plying a  corresponding  portion  of  alkali ;  and  the  passive,  (1)  as- 
sisting the  sense  of  taste,  (2)  favoring  the  expression  of  the 
voice,  and  (3)  clearing  the  mucous  membrane  of  the  mouth. 

CI.  Bernard,  the  distinguished  French  experimentalist,  has 
investigated  recently  the  action  of  saliva  in  digestion,  and  favors 
Beaumont's  views  of  the  mere  mechanical  agency  of  this  fluid ; 
opinions,  we  think,  sufficiently  controverted  by  Wright,  in  the 
experiments  just  quoted.     M.  Bernard,  however,  has  certainly 


184  THE  CHEMISTRY  OF  THE  MOUTH. 

advanced  our  knowledge  of  saliva,  as  will  be  seen  by  a  brief 
review  of  his  statements. 

We  have  already  mentioned  his  discovery  of  the  dilGference,  in 
physical  characters,  of  the  different  secretions  which  make  up 
the  common  saliva.  He  also  found  them  to  differ  in  their 
physiological  action,  that  of  the  parotid  and  sublingual  being  to 
saturate  the  food,  and  that  of  the  submaxillary,  by  its  glutinous 
consistence,  to  facilitate  deglutition.  To  confirm  this  opinion, 
he  made  an  opening  in  the  oesophagus  of  a  horse,  whence  he 
drew  the  alimentary  bolus  as  it  descended,  and  found  that  it 
had  increased  eleven-fold  by  the  imbibition  of  saliva.  He  next 
tied  Steno's  duct,  and  found  that  the  animal  required  forty-one 
minutes  to  masticate  what  before  had  demanded  but  nine 
minutes ;  and  the  mass,  when  Avithdrawn,  was  covered  with 
mucus  and  a  glutinous  fluid,  the  interior  being  dry  and  friable, 
and  the  whole  increased  in  weight  only  three  and  a  half  times. 
Water  seemed  to  promote  mastication  as  much  as  the  parotidean 
saliva,  this  latter  being  in  proportion  to  the  dryness  of  the  in- 
gested substance. 

As  to  its  action  upon  amylaceous  substances,  Bernard  main- 
tains it  to  be  very  gradual,  and  thinks  the  time  the  food  re- 
mains in  the  mouth  to  be  too  short  for  it  to  exert  any  other  than 
a  very  partial  transforming  influence  upon  it,  the  change  being, 
he  thinks,  arrested  by  the  acidity  of  the  gastric  juice.  He 
killed  a  dog,  fed  on  potatoes,  and  found  in  his  stomach  only  a 
trace  of  sugar,  but  much  unaltered  starch.  He  agrees  with 
Magendie  in  stating  that  neither  the  secretion  of  the  parotid 
nor  that  of  any  other  of  the  glands  taken  separately,  nor  yet 
when  mixed  with  each  other,  exert  any  transforming  influence 
upon  starch  ;  and  therefore  assigns  the  source  of  the  active 
principle  to  the  small  buccal  glands.  Bernard  grants  that 
ptyalin  possesses  this  property,  but  afiirms  that  it  is  not  peculiar 
to  the  salivary  secretion,  being  possessed  in  an  equal  degree  by 
many  animal  fluids,  as  the  water  in  which  buccal  mucous  mem- 
brane had  been  soaked,  the  serum  of  the  blood,  mucus  from  the 
nose  during  coryza,  &c.,  whence  he  concludes  that  the  salivary 
substance  does  not  difi"er  from  other  nitrogenous  substances  in  a 
state  of  change. 


SALIVA.  185 

We  have  preferred  to  give  the  above  brief  sketch  of  Bernard's 
views,  without  any  interpolations  of  our  own,  as  he  is  so  promi- 
nent an  observer,  and  has  so  especially  directed  his  attention  to 
the  digestive  fluids.  We  proceed  now  to  compare  his  results 
with  those  of  other  experimentalists  of  equal  ability  and  in- 
dustry. 

The  real  question  is  not  whether  the  ordinary  saliva  possesses 
a  metamorphic  power  over  starch,  for  that  is  universally  con- 
ceded. The  true  points  at  issue  are,  first :  Does  saliva,  as 
obtained  from  the  mouth,  possess  a  peculiar  power  of  this  kind, 
above  that  of  any  other  animal  fluid?  Secondly:  Is  this  power 
suspended  by  the  agency  of  the  gastric  juice,  as  Bernard 
affirms  ?  And,  thirdly :  Can  the  buccal  mucus  alone,  or  any 
one  of  these  secretions,  the  union  of  which  composes  the  ordi- 
nary mixed  saliva,  produce  this  efl"ect  in  a  sufficient  degree  to 
answer  the  purposes  of  digestion  ? 

In  reply  to  the  first  question,  we  ascertain  that  boiled  starch, 
mixed  with  fresh  saliva  and  agitated,  immediately  loses  its  vis- 
cidity, becoming  thin  and  watery.  Tested  with  iodine,  the 
mixture  is  not  rendered  blue,  an  experiment  which  establishes 
the  absence  of  starch.  Trommer's  test  exhibits  a  copious  pre- 
cipitate of  suboxide  of  copper,  precisely  as  it  does  in  all  solutions 
of  glucose. 

Now  it  is  well  known  that  other  substances  possess  this  power. 
Liebig  has  shown  that  gelatine  and  albuminous  and  gelatinous 
tissues,  when  moistened  and  exposed  to  the  atmosphere,  acquired, 
after  some  time,  the  property  of  producing  this  change.  Ma- 
gendie  discovered  that  infusions  of  cerebral  tissue,  heart,  lungs, 
and  spleen,  possessed  the  same  property ;  and  that  the  serum  of 
the  blood  at  104°  F.,  or  even  at  the  common  temperature  of  the 
body,  or  when  boiled  starch  was  thrown  into  the  veins,  could 
produce  the  same  metamorphosis.  Bernard,  therefore,  only 
repeated  these  well-known  experiments,  and  has  advanced 
nothing  at  all  conclusive  ;  because  a  fluid  which  of  itself  produces 
an  instantaneous  change,  cannot,  with  any  sort  of  fairness,  be 
compared  with  another  which  requires  time  and  admixture  with 
atmospheric  air  to  induce  the  same  change.  It  must  also  be 
borne  in  mind,  as  Dr.  Day  has  suggested,  when  speculating  upon 


186 


THE  CHEMISTRY  OF  THE  MOUTH. 


the  influence  of  these  different  animal  substances,  that  starch, 
when  exposed  to  the  air  for  a  length  of  time,  and  kept  at  a  high 
temperature,  undergoes  spontaneous  changes.  Even  those 
substances  which  act  most  rapidly  cannot  be  compared  with 
saliva,  as  will  be  seen  at  a  glance  by  consulting  the  following 
table,  embodying  the  results  of  a  very  extensive  series  of  re- 
searches made  by  Bidder  and  Schmidt,  with  a  view  of  determin- 
ing this  point. 


Substances  which  were  mixed  with  the  solution  of 
starch. 

1.  Saliva  of  adult  men. 

2.  Nasal  mucus  of  do. 

3.  Saliva  of  a  child  aged  four  mouths. 

4.  Saliva  of  dogs. 

5.  Pancreatic  juice  of  dogs. 

6.  Pancreatic  tissue  of  ditto. 

7.  Parotid  tissue  of  adult  pig. 

8.  Pancreatic  tissue  of  ditto. 

9.  Gastric  juice  of  dogs  which  had  been 

rendered  neutral  by  their  swallowing 
the  saliva. 

10.  Mucus  from  the  urinary  bladder  of  the 

pig- 

11.  Saliva  of  dog,  the  parotid  secretion  being 

excluded. 

12.  Pancreatic  tissue  of  a  dog,  ten  days  old. 

13.  Tissue  of   submaxillary  gland   of  adult 

pig- 

14.  Hepatic  tissue  of  the  same  animal. 

15.  Jluscular  coat  of  bladder  of  the  same 

animal. 

16.  Acid  gastric  juice  of  dogs  in  which  there 

were  no  epithelial  cells  from  the  buccal 
mucous  membrane. 

17.  Tissue  of  submaxillary  gland  of  dog  ten 

days  old. 

18.  Parotid  tissue  of  the  same  animal. 

19.  Mucus  from  the  mouth  of  a  dog  whose 

salivary  ducts  had  been  tied  a  fort- 
night previously. 

20.  Aqueous  extract  of  the  detached  buccal 

mucous  membrane  of  the  same  animal. 

21.  Parotid  tissue  of  the  same. 

22.  Tissue   of    submaxillary   gland   of    the 

same. 


Period  when  the  formation   of  sugar 
commenced. 

The  formation  of  sugar  began 
instantaneously,  but  it  was  only 
in  No.  1  that  the  whole  of  the 
starch  was  so  changed  that  iodine 
induced  no  blue  tmt ;  in  the  other 
experiments,  the  complete  change 
was  effected  in  various  times, 
the  longest  being  one  hour. 


30  minutes. 

20  minutes. 
40  minutes. 

1  hour. 

1  hour  and  20  minutes. 

1  hour  and  30  minutes. 

1  hour  and  30  minutes. 

2  hours  and  15  minutes. 
8  hours. 


After  3  or  4  hours  traces  of 
sugar  appeared,  but  the  solution 
of  starch  remained  thick  and 
viscid. 


SALIVA.  187 

Substances  which  were  mixetl  with  the  sclations  of  Period  when  the  fornjfitioii  of  sugar 

starch.  commeuced. 

23.  Parotid  secretion  of  the  dog.  ■(        Traces  of  sugar  appeared  after 

24.  Submaxillary  secretion  of  ditto.  J   "  hours. 

25.  Orbital  gland,  secretion  of  ditto.  No  trace  after  7  hours. 

26.  Saliva   after  the  exclusion  of  the  sub- 

maxillary secretion. 

27.  Acid  gastric  Juice  of  a  dog  whose  sub-  ■^ 

maxillary  and  parotid  ducts  had  been   I      No   trace   of   sugar   after   15 


No  susrar  after  2  hours. 


1 


tied.  J   hours 

"  There  are  two  points  to  be  noticed  in  regard  to  the  second 
of  these  experiments  :  in  the  first  place,  the  facility  with  which 
a  little  saliva  may  become  mixed  with  the  nasal  mucus,  in  sneez- 
ing and  similar  movements ;  and,  in  the  second,  the  circumstance 
that,  in  other  similar  experiments  with  nasal  mucus,  the  change 
did  not  commence  until  after  a  quarter  of  an  hour,  or  even  a 
longer  space  of  time  had  elapsed."* 

Thus,  it  will  be  seen  that  onr  first  question  must  be  answered 
in  the  affirmative. 

The  difficulty  in  regard  to  the  second  question,  arises  from  the 
notion  of  the  necessity  of  alkalinity  to  the  due  performance  of 
this  peculiar  function  of  the  saliva.  It  can  be  shown,  however, 
that  this  is  not  essential.  Jacubowitsch  and  Frerichs both  assert 
that  acid  saliva  acts  as  readily  on  starch  as  does  the  alkaline 
liquid.  Lehmann  examined  this  question,  by  acidifying  saliva 
with  acetic,  sulphuric,  hydrochloric,  and  nitric  acids,  and  always 
found  that  sugar  was  formed,  when  boiled  starch  was  subjected 
to  the  action  of  the  acid  saliva.  He  came  to  the  conclusion 
that  acids  do  not  impede  the  action  of  saliva  or  starch,  but  thatj 
whether  the  secretion  be  acid  or  not,  it  acts  with  equal  energy 
at  equal  temperatures. 

The  question  of  the  action  of  gastric  juice,  therefore,  so  far  as 
regards  its  mere  acid  properties,  may  be  considered  as  settled. 
Unfortunately,  however,  there  is  still  much  diversity  of  opinion 
among  eminent  chemists,  as  to  its  ascertained  eifects  on  the 
metamorphic  process.  Thus,  Jacubowitsch,  Frerichs,  and  Bence 
Jones,  are  positive  that  this  process  goes  on  after  the  admixture 
of  the  insalivated  morsel  with  the  gastric  juice,  and  Lehmann 

*  Dr.  G.  E.  Day,  in  Brit,  and  Fur.  Med.-Chir.  Rev.  for  July,  1850. 


188  THE  CHEMISTRY  OF  THE  MOUTH. 

and  Carpenter  indorse  the  statement.  The  balance  of  evidence 
and  of  authority  inclines  to  this  side.  But,  on  the  other  hand, 
we  find  facts  that  seem  to  contradict  it,  elicited  by  observers  of 
the  highest  eminence,  Bidder  and  Schmidt  among  them. 

The  following  experiments  have  been  made  by  Jacubowitsch : — 

Pure  filtered  gastric  juice,  obtained  from  a  gastric  fistula  in  a 
dog,  having  a  strong  acid  reaction,  and  containing  no  morpholo- 
gical elements,  was  neutralized  with  strongly  alkaline,  filtered 
human  saliva,  and  mixed  with  freshly  boiled  starch. 

Another  portion  of  the  same  gastric  juice  was  mixed  with  the 
same  saliva,  till  its  reaction  was  decidedly  acid,  and  this  was 
also  mixed  with  a  fresh  decoction  of  starch. 

Both  mixtures,  after  standing  for  two  hours  at  a  temperature 
of  about  100°  Fah.,  plainly  indicated  the  presence  of  sugar  on 
the  application  of  Trommer's  test. 

Other  experiments  were  instituted,  and  the  result  of  the 
whole  of  them,  as  summed  up  by  Jacubowitsch  is  that  the  gastric 
juice  does  not  impede  the  metamorphic  action  of  saliva  on  starch. 
Bidder  and  Schmidt  confirm  this  statement,  as  well  as  that  of 
Lehmann,  already  quoted,  with  regard  to  the  acidity  of  the  saliva. 
•  So  far,  all  these  distinguished  observers  are  fully  agreed,  but 
on  a  question  which  seems  to  be  identical,  viz.  the  presence  of 
sugar  in  the  stomach,  after  a  meal  of  starch  has  been  taken,  we 
find  them  to  difi"er  in  their  statements. 

Bidder  and  Schmidt  found,  for  example,  that  when  the  gastric 
fluid  is  alkaline,  in  consequence  of  the  quantity  of  saliva  which 
has  been  swallowed,  as  happens  with  animals  fed  after  a  long 
fast,  the  starch  is  immediately  changed ;  but  when  it  is  strongly 
acid  and  contains  little  or  no  buccal  epithelium,  it  does  not  begin 
to  affect  a  solution  of  starch  in  less  than  an  hour  and  a  half,  and 
then  only  slightly.  Here,  however,  the  action  of  the  saliva  is 
not  arrested,  but  only  impeded  by  the  extreme  dilution.  This, 
and  not  the  acidity,  is  probably  the  cause  of  the  delay.  These 
experiments  would  seem  to  show  that  the  rapidity  of  the  meta- 
morphosis is  directly  proportioned  to  the  quantity  of  saliva  pre- 
sent in  the  stomach. 

By  another  series  of  experiments,  these  same  observers  are 
led  to  conclude  that  sugar  is   often  absent  in  the  stomachs  of 


SALIVA.  189 

animals  fed  on  starch.  Hence,  Dr.  Day  remarks,  the  sugar, 
■which  must  have  been  formed  in  the  mouth,  has  either  been 
immediately  converted  into  lactic  acid,  and  so  lost  in  the  gastric 
juice,  or  else  it  has  been  immediately  absorbed.  He  inclines  to 
the  latter  opinion,  because  we  have  positive  proof  that  the 
stomachs  of  neither  herbivora  nor  carnivora  possess  the  property 
of  instantaneously  converting  sugar  into  lactic  acid.  The  ex- 
periments alluded  to  were  performed  by  introducing  boiled 
starch  into  the  stomachs  of  dogs,  sheep,  and  rabbits.  In  no 
instance  did  any  conversion  into  sugar  take  place. 

On  the  other  side,  we  learn  from  Frerichs,  that,  in  at  least 
fifty  experiments  on  men,  quadrupeds,  and  birds,  sugar  was 
always  present  in  the  filtered  gastric  fluid.  Jacubowitsch,  by  a 
series  of  well-devised  experiments,  seems  to  have  settled  the 
question.  He  gave  boiled  starch  to  a  dog  which  had  been  kept 
fasting  for  twelve  hours.  Through  a  previously  established 
gastric  fistula  he  withdrew  the  contents  of  the  stomach,  some 
four  or  five  hours  after  the  meal,  and  invariably  found  that  all 
the  starch  had  been  converted  into  sugar.  As  a  complementary 
experiment,  he  tied  the  parotid  and  submaxillary  ducts  of 
another  dog,  also  laboring  under  gastric  fistula,  and  fed  him  on 
boiled  starch.  This  animal  had  also  been  kept  fasting  for 
twelve  hours.  On  removing  the  contents  of  the  stomach,  at 
intervals  of  about  an  hour,  for  nine  hours  and  a  half  after  the 
meal,  he  found,  on  the  application  of  Trommer's  test  of  the  mi- 
croscope and  of  iodine,  that  no  sugar,  nor  even  dextrine,  had  been 
formed.  Frequent  repetitions  of  the  experiments  led  to  the 
same  results. 

The  discrepancy  between  the  statements  of  Bidder  and 
Schmidt  and  those  of  Jacubowitsch,  is  not  so  great  as  would  at 
first  sight  appear.  We  have  not  been  able  to  procure  their 
original  treatise,  and  have,  therefore,  been  compelled  to  rely 
upon  Dr.  Day's  analysis  of  it,  in  his  admirable  article  on  the 
Chemistry  of  Digestion,  already  so  largely  quoted  in  the  present 
chapter.  From  that,  it  would  appear  that  the  experiments  of 
Bidder  and  Schmidt  were  performed  by  introducing  the  starch 
directly  into  the  stomach,  by  means  of  elastic  tubes,  or  through 
a  gastric  fistula.      Jacubowitsch,  on  the  contrary,  fed  his  dogs 


190  THE  CHEMISTRY  OF  THE  MOUTH. 

on  the  boiled  starch,  so  that  he  eifected  the  natural  and  intimate 
admixture  of  the  saliva  with  the  food.  Every  particle  of  the 
starch  was  thus  brought  into  contact  with  the  ferment,  which 
was  transmitted  into  the  stomach  along  with  the  bolus.  His 
dogs  also  had  fasted,  so  that  they  had  abundance  of  saliva.  In 
the  experiments  of  Bidder  and  Schmidt,  however,  this  intimate 
admixture  did  not  take  place  ;  the  natural  stimulus  of  feeding 
was  not  applied  to  the  glands,  so  that  the  due  amount  of  saliva 
was  not  obtained ;  the  substance  was  introduced  in  such  a  way, 
that  no  action  whatever  could  take  place  except  upon  the  surface; 
and,  finally,  the*  only  saliva  which  could  act  upon  the  starch  was 
that  which  the  animals  might  have  swallowed.  Now,  from  the 
habits  of  dogs,  this  could  not  have  been  present  in  any  great 
quantity.  From  these  considerations,  it  does  not  appear  possi- 
ble to  institute  a  comparison  between  these  two  sets  of  experi- 
ments. The  difference  of  the  circumstances  attending  the  dif- 
ferent observations,  is  so  great,  that  Jacubowitsch's  deductions 
cannot  be  affected  by  the  experiments  of  his  preceptors. 

It  must  also  be  borne  in  mind  that  these  results  of  Bidder  and 
Schmidt  have  not  been  confirmed  by  other  observers.  Leh- 
mann,  experimenting  in  the  same  way,  obtained  totally  difi'er- 
ent  results.  He  always  found  sugar  in  the  stomach  of  the  ani- 
mal in  ten  or  fifteen  minutes  after  the  bolus  of  starch  had  been 
introduced.  Farthermore,  Dr.  Day,  the  translator  of  his  work, 
informs  the  public  that  in  his  third  volume,  the  English  transla- 
tion of  which  has  not  yet  been  published,  in  reviewing  the  results 
obtained  by  Bidder  and  Schmidt,  he  adheres  to  the  opinion  he 
first  advanced. 

We  think,  therefore,  that  a  due  weighing  of  the  evidence  ad- 
duced on  both  sides  will  compel  us  to  answer  the  second  question 
in  the  negative. 

The  tliird  question  divides  itself  into  two  parts.  The  first 
part  of  it,  which  relates  to  the  action  of  buccal  mucus,  has 
already  been  answered  by  the  experiment  of  Jacubowitsch, 
which  has  just  been  detailed.  That  shows  conclusively  that  the 
secretion  of  the  buccal  mucous  membrane  possesses  not  the 
slightest  influence  over  the  metamorphosis  of  starch,  a  result 
confirmed  by  Bidder  and  Schmidt  in  the  experiments,  No.  19 
and  20,  which  we  have  given  in  the  above  table. 


SALIVA.  191 

Where,  then,  does  this  saccharifying  power  reside  ?  Mialhe 
obtained  his  salivary  diastaste  by  precipitating  human  saliva 
with  absolute  alcohol.  Ptyalin,  mucus,  and  salts  must  have 
been  mingled  together  in  this  precipitate.  The  discoverer 
affirmed  that  so  powerful  was  the  action  of  this  so-called  diastase, 
that  one  part  of  it  readily  effects  the  metamorphosis  of  8,000 
parts  of  starch  at  a  temperature  of  37°.  Lehmann  has  totally 
failed  to  detect  such  a  potent  energy,  and  comes  to  the  conclu- 
sion that  "  the  metamorphosing  force  is  neither  concentrated  in 
the  admixture  of  substances  indicated  by  Mialhe  nor  by  myself, 
nor  yet  in  any  other  part  of  the  extractive  matters  of  the  saliva." 

Where,  then,  does  this  power  reside  ?  Magendie  and  Rayer 
found  that  the  parotid  secretion  of  the  horse  exerted  no  influence 
upon  starch.  Marshall  and  Garrod,  however,  in  experimenting 
on  the  fluid  derived  from  a  Stenonian  fistula  in  the  human  sub- 
ject, found  that  it  could  convert  starch  into  sugar.  Bernard 
found  that,  in  dogs,  neither  the  submaxillary  nor  the  parotid 
secretion  possessed  any  such  power.  Bidder  and  Schmidt  con- 
firm his  statement  on  this  point,  but  oppose  his  views  in  regard 
to  buccal  mucus,  as  we  have  already  seen.  They  found  that 
the  saccharifying  power  resides  in  no  one  of  these  secretions. 

Jacubowitsch,  after  satisfying  himself,  by  the  experiments  we 
have  already  detailed,  of  the  inactivity  of  the  buccal  mucus  by 
itself,  tied  the  ducts  of  a  single  pair  of  glands,  allowing  the 
secretion  of  the  others  to  mix  with  the  mucus  of  the  mouth.  It 
mattered  not  whether  the  secretion  of  the  submaxillaries  or  that 
of  the  parotids  was  thus  cut  off ;  in  either  case,  starch  digested 
with  the  dog's  saliva  was  converted  into  sugar  in  the  course  of 
five  minutes.  An  artificial  mixture  of  either  of  the  secretions 
with  the  buccal  mucus  possessed  the  same  power,  but  no  sugar 
was  produced  when  starch  was  digested  in  a  mixture  of  the 
submaxillary  and  the  parotid  secretions. 

Bidder  and  Schmidt  have  repeated  these  experiments,  and 
their  results  differ  somewhat  from  those  of  Jacubowitsch.  They 
found,  for  example,  that  parotid  saliva,  when  mixed  with  pure 
buccal  mucus,  exerted  no  very  marked  influence  over  the  meta- 
morphosis of  starch  ;  while  a  mixture  of  the  submaxillary  secre- 
tion with  the  mucus  acted  as  powerfully  as  common  saliva. 


192  THE  CHEMISTRY  OP  THE  MOUTH. 

Their  results,  in  regard  to  these  points,  are  summed  up  by 
Dr.  Day  in  these  words  : — 

"  1.  They  agree  with  Bernard  in  regarding  the  parotids  as 
glandes  aquipares ;  in  short,  as  yielding  a  secretion  which  is 
unquestionably  intended  to  moisten  and  saturate  the  dry  food, 
but  whose  principal  object  is  connected  with  the  general  meta- 
morphosis of  the  fluids  within  the  body,  and  which  is  devoid  of 
any  marked  action  on  starch. 

"  2.  By  the  union  of  the  submaxillary  secretion  and  that  of 
the  buccal  mucous  membrane,  there  is  formed  that  peculiar  fer- 
ment which  almost  instantaneously  converts  starch  into  sugar. 
This  active  principle  is  not  contained  in  the  cells  or  other  solid 
particles  suspended  in  the  saliva,  for  the  filtered  fluid  exhibits 
an  undiminished  force ;  and,  indeed,  this  property  is  not  de- 
stroyed when,  by  the  addition  of  a  little  alcohol,  we  precipitate 
the  mucus,  and  (entangled  in  it)  these  solid  particles." 

It  may  be  observed  here  that,  in  young  children  and  young 
animals,  in  whom  the  secretion  of  saliva  is  limited,  or  altogether 
absent,  this  metamorphic  action  is  very  feeble.  In  very  young 
infants  there  is  no  secretion  of  saliva  at  all.  If  equal  parts  of 
the  saliva  of  an  adult  and  of  a  child  at  the  breast  be  mixed  with 
starch,  it  will  be  found  that  while  the  action  commences  almost 
instantaneously,  it  is  completed  in  very  different  times.  When 
the  saliva  of  the  adult  man  is  used,  the  change  is  over  almost 
immediately,  while,  Avhen  that  of  the  child  is  mixed  with  starch, 
the  process  occupies  a  full  hour. 

According  to  Lehmann,  cane-sugar,  gum,  bassorin,  and  cellu- 
lose remain  unchanged  in  the  saliva ;  yet,  in  certain  species  of 
sugar,  long-continued  digestion,  at  a  high  temperature,  produces 
lactic  and  butyric  acids.  Recent  researches  show  that  no 
other  action  than  comminution  and  separation  of  particles  is 
effected  by  saliva  upon  albuminous  and  gelatigenous  food. 

Kletzinsky  has  investigated  the  influence  of  sulpliocyanide  of 
'potassium  upon  digestion.  He  found  that,  when  amylaceous 
and  albuminous  bodies  were  digested  with  very  dilute  solutions 
of  this  salt,  at  a  temperature  of  100°  or  110°,  no  change  took 
place.  Sugar  was  not  found,  nor  was  albumen  dissolved.  Sugar, 
with  which  yeast  was  mixed,  did  not  ferment  in  the  presence  of 


SALIVA.  193 

the  sulpliocyanide,  and  healthy  saliva  exerted  the  same  retarding 
influence,  while  that  of  mercurial  ptjalism  had  no  such  pro- 
perty. Certain  low  fungous  growths,  such  as  the  Oidium  auran- 
tiacum,  and  the  Penicilium  glaucum,  were  destroyed  by  this  salt. 
Children,  who  suffered  with  fungous  formations  in  their  mouths, 
were  found  to  secrete  saliva  in  which  this  salt  could  hardly  be 
detected.  The  opinion  of  this  observer  is,  that  the  function  of 
the  sulphocyanide  of  potassium  is  to  check  too  rapid  decomposi- 
tion and  the  formation  of  fungous  growths  within  the  system. 

Liebig  thinks  that  saliva  may  be  designed  to  convey  atmo- 
spheric air  into  the  stomach  and  intestines.  Some  objection  has 
been  made  to  this  opinion,  and  certain  experiments  opposed  to 
it  have  been  cited ;  but,  as  Lehmann  remarks,  they  "  were  not 
conducted  with  such  accuracy  as  to  exclude  all  access  of  oxygen, 
and  they  cannot  therefore  be  advanced  as  sufficient  evidence 
against  the  accuracy  of  Liebig' s  vieAV.  There  are,  moreover,  as 
we  know,  certain  processes,  as,  for  instance,  the  vinous  ferment- 
ation, in  which  it  requires  the  greatest  exactitude  to  demon- 
strate the  necessity  of  a  slight  access  of  oxygen.  Then,  again, 
the  fact  that  only  mixed  saliva,  that  is  to  say,  saliva  which  has 
been  in  contact  with  atmospheric  air,  is  capable  of  metamor- 
phosing starch,  speaks  rather  in  favor  of  Liebig's  view  than 
against  it.  Even  if  the  oxygen,  which  undoubtedly  passes  into 
the  primae  viae  with  the  saliva,  exerts  no  effect  upon  the  process 
of  digestion  in  the  stomach,  the  use  of  this  gas  in  the  intestinal 
canal  may  readily  be  understood,  although  it  cannot  be  specially 
demonstrated.  We  know  that  gases  are  present  in  the  intestinal 
canal,  and  that  these  gases  are  rich  in  carbonic  acid,  and  often, 
also,  in  hydrogen  compounds.  The  formation  of  the  latter, 
whose  passage  into  the  blood  would  be  followed  by  very  injurious 
results,  must  necessarily  be  greatly  limited  by  the  presence  of 
free  oxygen.  According  to  the  laws  of  the  diffusion  of  gases, 
the  presence  of  oxygen  in  the  intestines  must  diminish  the  with- 
drawal of  oxygen  from  the  blood,  and  the  supply  of  carbonic 
acid  and  hydrogen  to  that  fluid."* 

*  Physiological  Chemistry,  ii.  37, 

13 


194  THE  CHEMISTRY  OF  THE  MOUTH. 


CHAPTER    III. 

ON  THE  MORBID  CHANGES  OF  SALIVA. 

Dr.  Samuel  Wright,  whose  classification  will  be  followed  in 
this  chapter,  gives  the  following  table  of  salivary  diseases: — * 

Deficient  saliva. 

Redundant  saliva  (a.  Spontaneous;  /3.  Excited). 

Fatty  saliva. 

Sweet  saliva. 

Albuminous  saliva  (a.  Transparent ;  )3.  White). 

Bilious  saliva. 

Bloody  saliva. 

Acid  saliva. 

Alkaline  saliva  (a.  Fixed  alkali ;  /3.  Ammoniacal). 

Calcareous  saliva. 

Saline  saliva. 

Puriform  saliva. 

Fetid  saliva. 

Acrid  saliva  (a.  Per  se;  |3.  From  foreign  matters). 

Colored  saliva. 

Frothy  saliva. 

Urinary  saliva. 

Gelatinous  saliva. 

Milky  saliva. 

DEFICIENT    SALIVA. 

Saliva  may  become  deficient  temporarily  from  causes  purely 
physiological.  This  secretion  is  subject  to  the  same  laws  which 
govern  all  the  others.  Among  these,  none  is  better  known  than 
the  arrest  of  the  action  of  glands  in  consequence  of  some  strong 
mental  emotion.  The  insane,  who  live  in  a  perpetual  state  of 
emotional  excitement,  are  remarkable  for  the  general  torpor  of 

*  Lehmann  objects  to  this  as  an  unchemical  classification,  but  it  is  valu- 
able as  a  nosological  arrangement,  and  has  therefore  been  retained. 


ON  THE  MORBID  CHANGES  OF  SALIVA.  195 

the  secernents.  Narcotics  and  stimulants,  which  act  especially 
upon  the  emotional  centres,  suspend  the  secretions. 

A  familiar  example  of  this  mode  of  action  upon  the  salivary 
glands,  is  the  extreme  dryness  of  the  mouth  and  throat  to  which 
the  public  speaker  who  makes  his  maiden  harangue  is  notoriously 
subject.  The  rice  ordeal  among  the  Hindoos,  is  another  illus- 
tration of  the  same  fact.  This  is  commonly  employed  for  the 
detection  of  a  thief,  and  is  practised  in  this  way  :  The  suspected 
parties  are  placed  in  a  ring,  the  detector  being  in  the  centre. 
A  handful  of  rice  is  then  given  to  each  individual.  All  are 
ordered  to  chew  it  for  a  given  length  of  time,  and  to  reject  it 
upon  a  leaf  or  clean  piece  of  bark.  The  different  pallets  are 
then  examined,  and  should  one  of  them  be  unmoistened  by  saliva, 
the  unfortunate  person,  from  whose  mouth  it  came,  is  immediately 
seized  as  guilty  of  the  crime  alleged.  This  test  may  occasion- 
ally have  subserved  the  ends  of  justice,  particularly  if  the  cul- 
prit were  thoroughly  convinced  of  the  infallibility  of  the  method. 

Morbid  deficiency  of  saliva  may  arise  from  obstruction  of  the 
ducts,  from  inactivity  of  the  glands,  and  from  disorder  of  the 
stomach.  Obliteration  of  the  ducts  leads  to  the  disease  called 
ranula,  which  is  a  distension  of  a  duct  by  its  proper  secretion 
on  account  of  a  closure  of  its  natural  outlet.  This  closure  may 
be  congenital,  or  dependent  upon  tumors  pressing  upon  the  ducts, 
or  on  calculi  closing  them.  These  will  be  considered  in  a  sepa- 
rate chapter.  We  shall  only  say  here  that  the  sublingual  gland 
is  most  subject  to  them. 

A  distinction  must  be  made  between  common  and  encysted 
ranula.  The  contents  of  the  former  variety  are  only  saliva  as 
it  comes  from  the  glands ;  those  of  the  latter  are  albumen,  mu- 
cus, and  some  salts,  largely  diluted  with  water.  Gmelin  states  it 
to  be  water  94.6,  solid  matter,  5.4.  The  latter  consisted  of 
albumen,  extractive  matter,  and  the  salts  of  the  blood. 

Gorup  Besanez  has  analyzed  the  fluid  of  ranula  with  the  fol- 
lowing result : — 

Water 95.029 

Traces  of  fat  and  chloride  of  sodium        .  1.0(32 

Aqueous  extractive  matter      .         .         .  0.923 

Albuminate  of  soda         ....  2.98G 


196  THE  CHEMISTRY  OF  THE  MOUTH. 

Under  the  microscope  blood  and  exudation  corpuscles  were 
observed,  none  of  the  ordinary  characters  of  saliva  appearing.* 

Inactivity  of  the  glands  is  common  in  old  age,  but  is  occasion- 
ally found  in  persons  otherwise  in  full  health  and  vigor.  As  it 
is  a  purely  local  affection,  local  stimulants  will  generally  be  suf- 
ficient entirely  to  relieve  it. 

Disease  of  the  stomach,  especially  obstinate  indigestion,  is 
often  accompanied  by  a  disagreeable  dryness  of  the  mouth  de- 
pendent upon  salivary  deficiency.  It  is  usually  relieved  by 
tonics,  assisted,  if  necessary,  by  local  stimulants. 

REDUNDANT    SALIVA. 

Redundant  saliva  may  be  spontaneous^  the  fluid  remaining 
healthy ;  or  excited^  the  secretion  being  depraved  by  an  altera- 
tion in  its  constituents  or  by  the  presence  of  foreign  matter. 

It  is  present  in  infants  sometimes  from  birth,  sometimes  even 
in  the  foetus,  but  is  most  common  as  an  accompaniment  of  denti- 
tion. It  is  not  our  purpose  to  go  into  a  regular  pathological 
history  of  these  diseases.  We  consider  them  only  as  they  bear 
upon  the  chemical  history  of  this  fluid,  and  as  throwing  light 
upon  the  various  influences  of  the  secretion  on  the  teeth. 

The  specific  gravity  of  the  saliva  in  infantile  ptyalism  is  1003.1 
to  1005.  It  is  oftener  deficient  in  ptyalin  and  in  sulphocyanogen 
than  the  saliva  of  adults.  Being  generally  produced  in  local 
asthenia,  it  is  liable  to  an  occasional  variation  in  quality,  con- 
sisting in  a  predominance  of  its  albuminous  constituent.  "  I 
have  known  this,"  says  Dr.  Wright,  "  to  equal  3  per  cent."t 

Drivelling  belongs  to  the  other  end  of  life,  and  is  an  emi- 
nently asthenic  disease.  It  is  also  found  in  idiots.  Wright 
says  he  has  seen  the  specific  gravity  of  the  discharged  saliva  as 
low  as  1001.1;  often  1003,  and  never  above  1005.  "It  is  com- 
monly clear  and  transparent,  like  water,  and  seldom  has  the  blue 
tinge  which  distinguishes  the  healthy  secretion.  It  froths  very 
little  when  agitated,  is  often  deficient  in  albumen,  and  contains 
less  ptyalin  and  sulphocyanogen  than  natural ;  the  latter  I  have 

*  Rces.     Article  Saliva,  ia  Cyclopaidia  of  Anatomy  and  Physiology, 
t  Wright,  op.  cit. 


ON  THE  MORBID  CHANGES  OF  SALIVA.  197 

more  than  once  found  to  be  "wanting,  though  the  usual  saline 
constituents  were  present  in  their  accustomed  quantity.  The 
secretion  is  sometimes  alkaline,  but  oftener  neutral.'' 

Vogel  has  examined  the  saliva  of  spontaneous  salivation,  and 
gives  this  table  : — 

Water 991.2 

Ptyalin,  osmazome,  fat,  and  albumen     .  4.4 

Salts  of  soda,  potash,  and  lime      .         .  4.4 

1000.0 

Mitscherlich  and  Guibourt  found  no  increase  in  the  solid  con- 
stituents, Avhile  the  sulphocyanogen  and  ptyalin  were  deficient. 

Though  in  gastric  diseases  the  saliva  is  usually  diminished, 
there  are  afi"ections  of  the  stomach  which  are  accompanied  by  a 
great  increase  in  the  flow  of  saliva.  Nausea,  for  example,  is 
always  attended  by  this  symptom.  So  is  hunger ;  so  is  appe- 
tite generally,  especially  when  stimulated  by  the  sight,  the  smell, 
or  even  the  thought  of  a  favorite  dish.  Pyrosis  has  been  usually 
supposed  to  arise  from  a  morbidly  increased  flow  of  fluid  from 
the  gastric  glands,  but  Dr.  Wright  [op.  cit.)  gives  reasons  for 
believing  that  the  flow  comes  chiefly  from  the  salivary  organs. 

He  derives  his  arguments,  first,  from  the  specific  gravity  of 
the  fluid,  which  he  quotes  from  Golding  Bird.  The  average  spe- 
cific gravity  of  the  fluids  of  gastrorrhoea  and  pyrosis  was  1.0097, 
and  that  of  saliva  1.0081.  The  lowest  saliva  was  1.0043,  the 
highest  1.0155,  while  the  lowest  pyretic  fluid  was  1.0058,  and 
the  highest  1.0209.  In  the  second  place,  he  states  that  the  re- 
action in  pyrosis  is  that  of  saliva.  He  experimented  on  nineteen 
specimens  in  which  the  reaction  was  strongly  alkaline  in  eleven, 
feebly  alkaline  in  three,  neutral  in  three,  and  acid  in  two.  In 
every  case  the  state  of  the  saliva  corrresponded  with  that  of  the 
ejected  fluid.  This  is  strengthened,  if  we  consider  and  appre- 
ciate the  difiiculty  of  supposing  the  stomach,  which  is  engaged 
regularly  in  secreting  an  acid  fluid,  should  suddenly  change  its 
action  and  make  an  alkaline  secretion,  and  then  again,  without 
any  apparent  reason,  return  to  acid  secretion  again. 

One  of  Dr.  Bird's  objections  to  this  theory  is  derived  from 
the   behavior  of  reagents.     Sesquichloride  of  iron,  according  to 


198  THE  CHEMISTRY  OF  THE  MOUTH. 

this  observer,  did  not  give  the  characteristic  blood-red  tinge 
■with  pyrotic  fluid,  but  only  an  orange  more  or  less  deep.  In 
reply  to  this,  Dr.  Wright  states,  that  the  sesquichloride  rarely 
gives  the  blood-red  color  with  saliva,  unless  an  alcoholic  solution 
of  the  dried  secretion  be  used,  because  the  animal  matters  pre- 
sent cloud  the  solution  and  obscure  the  tint.  Ptyalin,  he  regards 
as  characteristic  of  saliva,  and  he  asserts  that  he  has  rarely 
made  an  examination  of  the  liquid  ejected  in  pyrosis,  without 
finding  a  sufficiency  of  this  principle  to  convince  him  of  the  na- 
ture and  origin  of  the  secretion.  He  gives  the  following  analyses 
by  Dr.  Percy  as  evidence  in  favor  of  his  view  : — 

No.  I. 

Water 938.4 

Solid  matter,  consisting  of  mucus,  chloride  of  so- 
dium, free  soda,  and  a  trace  of  the  matter  upon 
which  depends  the  peculiar  and  characteristic 
odor  of  saliva  .....  16.6 

No.  II. 

Water 994.1 

Ptyalin        .......       a  trace. 

Matter  dissolved  by  alcohol  .         .         .  1.31 

Matter  left  after  treating  by  ether  and  alcohol ; 

mucus  with  a  trace  of  albumen           .         .           3.63 
Saline  matter ;    chlorides  of  potassium  and  so- 
dium, with  free  alkali  or  carbonate              .           2.88 
Loss 08 


1000.00 

Dr.  George  Wilson  has  published  an  analysis  of  the  fluid  of 
pyrosis,  in  which  he  coincides  with  Mr.  Goodsir,  in  representing 
the  most  remarkable  character  of  it  to  be  the  presence  of  a  small 
cryptogamic  plant,  sarcina  ventriculi.  The  organisms  are  in 
the  form  of  square  or  slightly  oblong  transparent  plates  of  a 
pale  yellow  or  brown  color,  varying  in  size  from  the  800th  to  the 
lOOOtli  of  an  inch.  They  were  made  up  of  cells  with  dissepi- 
ments, which  pressing  against  one  another  became  bulged  out  in 
the  middle,  so  that  the  organism  resembled  a  soft  bundle  bound 


ON  THE  MORBID  CHANGES  OF  SALIVA.  199 

with  cord  crossing  four  times  at  right  angles  and  at  equal  dis- 
tances. From  these  peculiarities  Mr.  Goodsir  gave  it  the  name 
of  sarcina,  a  "wool-pack.  The  chemical  reactions  of  the  fluid 
differed  from  those  just  quoted  from  Dr.  Wright.  It  was  strongly- 
acid,  and  found  to  contain  free  acetic,  hydrochloric,  lactic,  and 
carbonic  acids. 

PTTALISM. 

Artificial  ptyalism  is  most  commonly  produced  by  the  pre- 
parations of  mercury.  The  quantity  of  the  liquid  discharged 
under  the  operation  of  this  agent  is  extremely  variable.  Its 
chemical  composition  has  been  variously  stated. 

Observers  are  especially  divided  as  to  the  presence  of  mercury 
in  this  fluid.  Bostock,  Devergie,  and  Wright  could  not  detect 
it  by  the  most  delicate  tests.  Gmelin,  however,  obtained  it  by 
Smithson's  method,  which  is  a  modification  of  the  galvanic  test. 
A  large  quantity  of  saliva  was  treated  with  nitric  acid  and 
evaporated.  The  dry  matter  was  digested  in  nitric  acid  and 
dissolved  in  water,  the  fat  was  removed  by  filtration,  and  a 
stream  of  sulphuretted  hydrogen  passed  through  the  solution. 
The  precipitate  obtained  by  this  process  contains  sulphuret  of 
mercury ;  it  must  be  collected,  digested  in  nitro-muriatic  acid, 
evaporated,  dissolved  in  dilute  hydrochloric  acid,  and  a  bit  of 
goldleaf,  enveloped  in  tinfoil  or  encircled  by  fine  iron  wire, 
suspended  in  the  fluid.  The  gold  is  tarnished  if  mercury  is  pre- 
sent. No  tinfoil  should  be  used  which  has  not  been  itself  tested 
for  mercury.  The  tarnish  must  also  be  examined  ;  for  Taylor 
has  shown,  that  in  the  presence  of  free  hydrochloric  acid,  tin 
may,  by  galvanic  action,  be  precipitated  upon  gold.  The  foil 
should,  therefore,  be  made  into  a  cornet  and  introduced  into  a 
reduction  tube  of  narrow  caliber.  Heat  being  applied,  if  the 
stain  be  mercurial,  a  dew  of  minute  metallic  globules  will  collect 
upon  the  cool  part  of  the  tube.  Another  mode  of  examination 
more  simple  than  this  is,  to  let  fall  a  drop  of  dilute  nitric  acid 
upon  the  stain.  If  it  be  mercurial,  it  is  dissolved  ;  if  tin,  it  is 
rendered  white  and  opaque  from  the  formation  of  the  oxide  of 
that  metal. 

Lehmann  has  always  found  the  metal  in  the  fluid  of  mercurial 


200  THE  CHEMISTRY  OF  THE  MOUTH. 

ptyalism,  botli  by  dry  distillation  and  by  the  galvanic  test,  his 
little  battery  being  formed  of  two  pairs  of  very  minute  plates  of 
copper  and  zinc,  suspended  in  the  acidulous  solution.  He  thinks 
the  cause  of  failure  in  Wright,  and  those  who  think  with  him,  to 
be  twofold.  First,  they  have  often  examined  the  buccal  secretion 
only,  since,  in  the  first  stage  of  salivation,  this  constitutes  almost 
the  entire  bulk  of  the  sputa,  the  salivary  glands  being  affected 
later ;  and  secondly,  unless  the  evaporation  be  conducted  with 
very  great  caution,  the  mercury  readily  volatilizes  with  the 
aqueous  vapor. 

The  specific  gravity  of  the  saliva,  according  to  Wright,  is  in- 
creased prior  to  the  occurrence  of  actual  ptyalism.  He  attributes 
this  augmentation  of  density  to  an  excess  of  albumen,  rarely  of 
mucus,  and  regards  it  as  the  first  indication  of  the  action  of 
mercury  upon  the  salivary  glands,  preceding  fetor  and  the 
tumefaction  of  the  gums.  The  greatest  specific  gravity  he  met 
with  in  commencing  ptyalism,  was  1.059.  In  one  case,  in  which 
violent  salivation  set  in  six  hours  after  a  dose  of  five  grains  of 
calomel,  it  was  only  1.0048.  After  the  discharge  has  fairly 
commenced,  the  density  of  the  liquid  diminishes,  and  continues 
lowtill  the  action  of  the  glands  begins  to  diminish.  Gokling 
Bird  estimates  it  at  1.0043,  Thomson  at  1.0038,  and  Wright  has 
found  it  as  low  as  1.0015.  When  separated  from  the  shreds  of 
mucus,  which  occasionally  troubles  it,  it  is  nearly  as  limpid  and 
thin  as  water.  Generally,  as  the  excitement  of  the  glands  de- 
creases, the  secretion  thickens  and  contains  excess  of  fatty 
matter. 

The  sulphocyanide  of  potassium  is  very  variable  in  its  pro- 
portions, some  specimens  furnishing  not  a  trace  of  it,  while  from 
others  Wright  obtained  3  per  cent.  In  the  majority  of  instances 
he  observed  an  increase  of  sulphocyanogen. 

The  quantity  of  mucus  is  often  unnaturally  increased ;  fre- 
quently it  is  adventitious,  being  derived  from  the  mucous  mem- 
brane of  the  mouth,  which  becomes  detached,  and  is  then  par- 
tially dissolved  in  the  secretions.  "  The  specific  gravity  of  the 
fluid  is  thus  considerably  heightened,  and  its  transparency  dis- 
turbed. The  epithelium  is  at  first  suspended  like  nebuljB  in  the 
mass  of  fluid,  but  if  left  at  rest,  it  gradually  subsides  as  a  gray- 


ON  THE  MORBID  CHANGES  OF  SALIVA.  201 

ish  jelly-like  sediment,  and  leaves  the  supernatant  liquid  com- 
paratively clear.  At  other  times  the  ])roper  mucus  of  the  saliva 
is  unusually  abundant,  but  the  intermixture  is  so  perfect,  that, 
notwithstanding  the  increased  amount  of  animal  matter,  there 
is  no  observable  turbidity.  The  secretion  is  inordinately  viscid, 
does  not  drop  from  the  mouth  of  a  bottle,  but  runs  in  a  stream 
[en  masse),  and  is  not  easily  miscible  with  water.  It  does  not 
froth  more  than  common  when  agitated,  nor  does  boiling  furnish 
any  extra  coagulation.  I  have  more  than  once,  under  these 
circumstances,  remarked  the  entire  absence  of  albumen."* 
Often,  however,  the  saliva  of  mercurial  ptyalism  contains  albu- 
men in  excess. 

It  is  usually  increased  in  alkalinity,  and  thorouglily  trans- 
parent, though  sometimes,  as  already  intimated,  turbid  from  the 
admixture  of  mucus  and  epithelium.  It  froths  greatly  when 
agitated,  and  does  not  recover  its  clearness  readily  by  rest.  It 
absorbs  oxygen  rapidly,  decomposes  easily,  and  rarely  deposits 
any  sediment  till  this  last  change  has  commenced. 

The  quantity  of  ptyalin  is  often  increased,  whence  arises  the 
sharp,  penetrating  taste  and  smell  for  which  this  morbid  saliva 
is  so  remarkable.  Should  pus  mingle  itself  with  the  liquid,  jjfyaZm 
disappears,  and  the  pungent  odor  is  lost.  When  ptyalin  is 
abundant,  the  saliva  decomposes  with  unusual  rapidity,  evolving 
an  excess  of  ammonia.  The  reaction  is  almost  constantly  alka- 
line, and  Wright  makes  it  an  element  in  prognosis ;  the  change 
of  this  fluid  from  acidity  to  alkalinity,  in  febrile  and  inflamma- 
tory afl'ections,  being  often  the  first  sign  of  amendment.  The 
exceptions  to  alkalinity  are  scrofulous  and  scorbutic  cases,  and 
excessive  salivation.  In  the  latter  instances,  the  secretion  be- 
comes exceedingly  off"ensive,  and  loses  its  characteristic  proper- 
ties. It  is  usually  of  a  dark  brown  or  fawn  color,  sometimes 
intermixed  with  blood.  When  first  discharged,  it  is  opaque  from 
clouds  of  mucus  and  epithelium,  which  are  gradually  deposited 
as  a  bulky  sediment,  and  the  supernatant  liquor  is  left  clear,  and 
of  a  brownish  or  reddish  color.  "The  secretion  seldom  Qon- 
iom^  ptyalin,  and  is  often  also  deficient  in  sulphocyanogen.     It 

*  Wright,  op.  cit. 


202  THE  CHEMISTRY  OF  THE  MOUTH. 

readily  decomposes,  and  then  becomes  additionally  offensive,  and 
very  ammoniacal.  Its  odor  appears  to  depend  upon  a  fatty  mat- 
ter which  is  separable  by  ether  and  by  distillation.  This  saliva 
bears  little  resemblance  to  the  natural  secretion,  except  in  being 
furnished  by  its  glands.  It  exerts  no  digestive  action  upon 
starch,  and  is  very  liable  to  produce  nausea  or  vomiting,  if 
swallowed."* 

L'Heritier  gives,  as  the  mean  of  three  analyses  of  the  fluid 
of  mercurial  ptyalism  : — 

Water      .         .         .         970.0  in  place  of  986.5 
Organic  matters        .  28.6  "  12.6 

Inorganic  matters     .  1.1  "  1.9 

The  mean  amount  of  ptyalin  was  2.6.  The  increased  quan- 
tity of  organic  matters  he  accounts  for  by  the  increased  action 
of  the  buccal  mucous  membrane. 

Simonf  has  published  an  analysis  of  saliva  from  a  patient  who 
had  just  concluded  a  mercurial  course  of  four  weeks'  duration. 
It  had  an  acid  reaction  occasioned  by  the  presence  of  free  acetic 
acid.  It  was  very  viscid,  of  a  yellow  color,  and  possessed  a 
sickly,  disagreeable,  acid  smell.  No  mercury  was  found  in  it. 
After  evaporation  to  dryness,  all  the  acid  reaction  had  disap- 
peared, showing  the  absence  of  lactic  acid.  It  contained  a  very 
large  quantity  of  semifluid  fat,  a  considerable  amount  of  albu- 
men, and  traces  of  caseous  matter.  Many  fat  vesicles,  epithe- 
lium cells,  and  so-called  salivary  corpuscles,  were  visible  under 
the  microscope.     1000  parts  contained  : — 

Water 974.12 

Yellow  viscid  fat        .         .         .         .  6.94 

Ptyalin  with  extractive  and  traces  of  casein  3.60 
Alcohol  extract,  with  salts         .         .  7.57 

Albumen ......  7.77 

"  The  salts  consisted  of  a  large  preponderance  of  the  chlo- 
rides of  sodium  and  potassium,  associated  with  the  lactates  of 

*  Wright,  op.  cit. 

f  Animal  Chemistry,  302. 


ON  THE  MORBID  CHANGES  OF  SALIVA.  203 

soda  and  potash,  and  with  a  small  quantity  of  the  earthy  phos- 
phates. On  contrasting  this  saliva  with  the  normal  fluid,  we 
are  struck  with  its  large  amount  of  solid  constituents,  arising 
not  from  any  increase  of  the  ptyalin,  but  of  the  fat,  the  extract- 
ive matters,  the  albumen,  and  the  salts. 

Dr.  Wright  gives  three  analyses  of  this  fluid : — 

Water  ..... 
Ptyalin  .... 

Fatty  acid     .... 
Albumen  with  soda  and  albumi- 
nate of  soda 
Mucus  with  a  trace  oi  ptyalin 
Lactates        f  Potash  ^ 

Muriates      }  Soda      \  -         -  1-9  2.4  2.6 

Phosphates  (^  Lime    J 
Hydrosulphocyanates      .         .  3.  2,2  1.8 


No.  1. 

No.  2. 

No.  3. 

989.8 

988.7 

987.4 

1.7 

1.9 

.2.7 

a  trace. 

.4 

.7 

1.5 

.6 

1.3 

2.1 

3.8 

3.5 

1000.0    1000.0     1000.0 

In  the  analysis  No.  1,  the  sulphocyanide  of  potassium  was 
separately  estimated  and  found  to  be  .3  in  the  thousand  parts. 

Iodine  stands  next  to  mercury  as  a  general  sialagogue.  The 
mercurial  fetor  has  been  stated  by  some  observers  to  be  present 
in  this  form  of  salivation,  while  others  deny  that  there  is  either 
fetor,  sponginess  of  the  gums,  or  loosening  of  the  teeth.  The 
explanation  of  this  discrepancy  will  probably  be  found  in  the 
facts  recently  elicited  by  M.  Melsens's  researches.  This  accurate 
and  careful  observer  shows  that  mercury  may  remain  a  very 
long  time  in  the  system,  in  consequence,  probably,  of  its  pro- 
perty of  forming  insoluble  compounds  with  the  various  organic 
substances  of  which  the  body  is  composed ;  and  that  iodide  of 
potassium  is  capable  of  dislodging  it,  and  making  it  soluble,  so 
that  it  will  again  enter  the  current  of  the  blood,  and  may,  con- 
sequently, if  set  free  in  sufiicient  quantity,  produce  its  primary 
eifects  of  salivation,  erythema,  &c.  Dr.  Budd  relates  a  case  in 
which,  five  months  after  taking  mercury,  a  patient  was  violently 
mercurialized  in  this  way  by  iodide  of  potassium. 


20i  THE  CHEMISTRY  OF  THE  MOUTH, 

The  tendency  of  iodine  and  its  compounds  to  pass  off  through 
the  salivary  secretion,  has  ah'eady  been  mentioned.  Like  most 
other  substances,  however,  it  may  change  the  organ  of  elimina- 
tion, and  may  be  discharged  through  the  skin,  the  kidneys,  or 
even  by  means  of  the  fluid  evacuated  in  consequence  of  the 
operation  of  a  seton.  Under  circumstances  like  these,  its  elimi- 
nation by  the  salivary  glands  is  of  course  checked,  if  not  entirely 
suspended. 

Pare  iodic  salivation  differs  materially  from  that  produced  by 
mercury.  The  vascularity  of  the  mucous  membrane  of  the 
mouth  and  of  the  salivary  glands  may  be  unchanged,  but  oftener 
it  is  increased,  the  glands  especially  becoming  tumid  and  tender. 
The  secretion  itself  contains  an  unusual  amount  of  mucus  or 
albumen,  the  excess  of  one  or  other  of  these  elements  consti- 
tuting its  chief  deviation  from  the  healthy  state.  The  unplea- 
sant taste  of  iodine  is  often  perceived  in  the  secretion,  and  weight 
at  the  root  of  the  tongue,  aching  of  the  jaws,  and  singing  in  the 
ears  are  complained  of.  An  increased  flow  of  tears  and  of 
nasal  mucus  generally  accompanies  this  form  of  salivation. 

Other  halogens,  especially  chlorine  and  bromine,  have  been 
known  to  salivate.  Ptyalism  is  one  of  the  effects  of  arsenic, 
even  wdien  given  in  medicinal  doses.  Lead  and  antimony  are 
said  to  act  in  the  same  manner.  The  terchloride  of  gold  is  an 
undoubted  sialagogue,  and  some  obstetricians  even  fancy  that 
rubbing  the  gums  with  metallic  gold  facilitates  dentition  and 
increases  the  quantity  of  the  salivary  secretion.  A  host  of 
other  substances  have  been  asserted  to  exert  the  same  action. 
Among  them  are  found  opium,  conium,  belladonna,  nux  vomica, 
digitalis,  xanthoxylum,  and  hydrocyanic  and  nitric  acids.  Sulphur 
increases  the  quantity  of  sulphocyanogen,  as  already  stated, 
and,  sometimes  after  the  protracted  use  of  this  agent,  sulphur- 
etted hydrogen  has  been  liberated  by  the  addition  of  an  acid  to 
the  saliva.  The  action  of  local  sialagogues  in  increasing  the 
alkalinity  of  the  saliva  has  been  already  noticed. 

FATTY    SALIVA. 

In  addition  to  the  fatty  matter  found  in  healthy  saliva,  adven- 


ON  THE  MORBID  CHANGES  OF  SALIVA.  205 

titious  fat  is  often  present  in  this  secretion,  •which  is  consequently 
changed  in  appearance  and  properties. 

♦The  quantity  of  fatty  saliva  secreted  is  usually  less  than  that 
of  the  healthy  liquid ;  it  is  freer  and  more  abundant  in  the 
evening ;  it  has  a  greasy  taste  and  feel  in  the  mouth ;  when 
depraved,  it  is  often  very  offensive,  and  is  sometimes  compared 
to  castor-oil ;  it  imparts  a  sticky  or  slimy  sensation  to  the  whole 
mouth,  and  is  with  difficulty  rejected.  In  these  cases,  examined 
by  Wright,  from  whom  this  description  is  copied,  the  specific 
gravity  was  1.0098,  1.0107,  and  1.0113.  It  is  usually  frothy 
on  the  surface,  and  the  bubbles  disappear  very  slowly.  Its 
color  is  a  dull  or  yellowish  white,  of  variable  intensity,  never 
semi-transparent  and  bluish  like  healthy  saliva.  Its  smell  is 
greasy  and  sickly,  never  normal.  The  ptyalin  and  the  sulpho- 
cyanogen  are  sometimes  altogether  wanting.  It  absorbs  oxygen 
sparingly,  and  exerts  but  a  feeble  action  upon  starch.  It  im- 
perfectly converts  it  into  gum,  and  produces  no  sugar. 

Wright's  method  of  analyzing  this  variety  of  morbid  saliva 
was  carefully  to  dry  the  specimen  and  exhaust  the  residue  with 
sulphuric  ether.  On  evaporating  the  ethereal  solution,  we  have 
fat,  ptyaJin,  and  sulphocyanide  of  potassium.  The  last  two  are 
dissolved  by  washing  in  cold  water,  and  pure  fatty  matter 
remains,  which  must  be  collected,  dried,  and  weighed. 

His  analysis  of  what  he  considered  an  excellent  specimen  of 
fatty  saliva  is — 

Water 987.4 

Ptyalin       ......  .7 

Adventitious  fatty  matter  and  fatty  acid         3.9 

Albumen  with  soda,  and  albuminate  of 

soda         ......  1.5 

Sulphocyanide  of  potassium  .         .   a  trace. 

Mucus 2.4 

Lactates  f  Potash  ^ 

Muriates        J  Soda      I  .         .  1.8 

Phosphates      (^  Lime    J 

Loss 2.3 

1000.0 


206  THE  CHEMISTRY  OF  THE  MOUTH. 

This  state  of  the  saliva  accompanies  disorders  of  the  aliment- 
ary canal,  whether  these  are  primary  or  consequent  upon  some 
other  affection.  In  the  saliva  of  a  phthisical  patient,  Landerer 
found  a  great  number  of  small  fat-globules  aggregated  into  a 
viscid  mass.  These  globules  exhibited  the  properties  of  oleic  acid. 
Wright  found  it  present  in  phthisis,  chlorosis,  diabetes,  jaundice, 
smallpox,  the  dyspepsia  of  gluttony  and  of  intoxication,  and  in 
poisoning  by  ergot  of  rye.  Should  it  be  persistent,  he  regards 
it  as  pathognomonic  of  disordered  function  of  the  lining  mem- 
brane of  the  stomach  and  bowels. 

SWEET   SALIVA. 

This  is  a  disease  which  is  noticed  in  most  of  the  larger  sys- 
tematic works  on  the  practice  of  medicine.  It  is  found  in  con- 
junction with  a  variety  of  morbid  affections.  The  same  state  of 
the  system  which  gives  rise  to  diabetes  may  produce  it,  and, 
indeed,  the  two  affections  are  often  coincident.  But  it  often 
occurs  independently  of  the  urinary  disorder,  and  in  subjects 
in  other  respects  perfectly  healthy.  Robust,  active  children 
and  adults  are  sometimes  attacked  with  it  in  the  early  part  of 
the  day,  particularly  if  the  stomach  be  empty.  It  more  fre- 
quently, however,  is  found  in  conjunction  with  gastro-intestinal 
irritation,  and  other  forms  of  depraved  digestion  and  assimila- 
tion. 

"  It  is  either  of  a  light  fawn  or  a  dead  white  color,  with 
mucous  nebulae  ;  froths  easily  by  agitation,  but  its  bubbles  are 
not  permanent,  scarcely  affords  a  coagulum  by  heat,  is  either 
acid  or  neutral  to  test  paper,  has  a  mucous  or  syrupy  smell, 
which  is  increased  by  an  elevation  of  temperature ;  decomposes 
readily,  and  furnishes  acetic  acid." 

"  It  imparts  a  sense  of  sweetness  to  the  tongue  ;  not  always 
agreeable,  but,  for  the  most  part,  mawkish  or  sickly ;  sometimes 
followed  by  a  secondary  taste  of  bitterness,  like  woody  night- 
shade ;  and,  again,  by  a  sense  of  astringency.  It  is  very  adherent 
to  the  tongue  and  mouth,  and  its  impression  is  often  lasting.  On 
its  accession  it  is  merely  complained  of,  but  its  continuance  is 
often  very  annoying,  and  occasionally  it  nauseates  distressingly." 


ON  THE  MORBID  CHANGES  OF  SALIVA. 


20T 


It  is  analyzed  by  first  filtering,  as  usual,  and  after  separating 
the  2^iyC'^in  and  fatty  acid  with  ether,  as  before  directed,  passing 
distilled  water  through  the  filter  to  complete  exhaustion.  The 
saccharine  matter  is  only  partially  soluble  in  water,  and  part  of 
it  is  therefore  found  in  the  filtrate  with  the  chlorides.  The  rest 
must  be  obtained  from  the  residue  by  exhaustion  with  boiling 
alcohol.  The  chlorides  are  decomposed  by  acetate  of  silver,  the 
liquid  filtered  from  the  chloride  of  silver,  the  filtrate  carefully 
evaporated  to  dryness,  and  the  dry  residue  weighed.  The  sugar 
and  acetic  acid  are  then  got  rid  of  by  incineration,  the  pure  soda 
left  must  be  weighed,  the  acetate  of  soda  allowed  for,  and  the 
sugar  estimated  by  difference.  On  fermentation  with  yeast,  the 
aqueous  solution  yields  a  notable  quantity  of  alcohol,  and  on 
evaporation  is  reduced  to  a  syrup. 


Wright's  analysis  of  sweet  saliva  is  : — 

Water 

986.9 
.3 

.2 
•       5.6 

Jr^tyaiin        ........ 

Fatty  acid 

Muco-saccharine  matter         .... 

Albumen  with  soda  and  albuminate  of  soda   . 

.4 

Mucus  with  a  trace  of  ptyalin 

2.6 

Sulpbocyanide      ...... 

Lactates       r  Potash  ^ 

a  trace. 

Muriates     ^  Soda     V 

1.9 

Phosphates  (.Lime    J 

Loss 

2.1 

1000.0 

The  fluid  analyzed  above  was  obtained  from  a  diabetic  patient 
in  whom  a  spontaneous  ptyalism  had  temporarily  occurred. 


ALBUMINOUS    SALIVA. 


The  normal  variation  in  the  quantity  of  albumen  in  saliva  is 
set  down  by  Wright  at  .02  per  cent,  for  the  minimum,  and  .5 
for  the  maximum.  Any  proportion  of  albumen  beyond  these 
limits,  either  way,  constitutes  disease. 


208  THE  CHEMISTRY  OF  THE  MOUTH. 

Albuminous  saliva  may  be  classed  under  two  heads,  the  trans- 
parent and  opaque  varieties.  The  first  of  these  is  almost  per- 
fectly transparent,  colorless,  and  untroubled  by  nebulre.  It  has 
less  2^f^(iiin  and  more  sulphocyanogen  than  the  healthy  secre- 
tion, is  very  tenacious,  froths  excessively  when  agitated,  and 
coagulates  at  212°.  Its  specific  gravity  and  alkalinity  are 
great.  It  decomposes  easily,  becoming  first  turbid,  then  mouldy 
and  ammoniacal.  Its  action  on  starch  is  not  so  decided  as  that 
of  healthy  saliva.  It  produces  the  same  quantity  of  gum,  but 
less  sugar  and  lactic  acid. 

The  opaque  variety  has  a  high  specific  gravity,  varying  from 
1.0168  to  1.0095.  It  is  milky  in  appearance,  absolutely  opaque, 
and  when  boiled,  coagulates  in  flakes,  which  subside,  leaving  a 
supernatant  fluid  like  whey.  There  is  but  a  small  quantity  of 
ptyalin  and  sulphocyanide  of  potassium  in  this  variety  of  albu- 
minous saliva.  It  is  always  strongly  alkaline,  has  a  mucous  or 
mouldy  smell,  froths  with  permanent  bubbles  when  agitated, 
absorbs  but  little  oxygen,  and  has  little  action  on  starch.  Dur- 
ing decomposition,  it  evolves  hydrosulphuret  of  ammonium,  and 
sometimes  hydrocyanic  acid.  The  quantity  of  albumen  varies. 
In  four  specimens,  Wright  found  .62,  .96,  1.01,  and  1.03  per 
cent,  respectively.  The  salivary  glands  are  always  in  a  disor- 
dered or  slusmish  condition  when  this  albuminous  saliva  is  ex- 
creted,  and  often  digestion  is  more  or  less  seriously  impaired. 
Mercury  and  iodine,  especially  the  last,  produces  this  disease  of 
the  secretion.  The  drunkard  and  the  glutton  are  peculiarly 
liable  to  it. 

BILIOUS    SALIVA. 

The  bile,  Avhen  once  absorbed,  or  not  eliminated  by  the  liver, 
tinges,  as  we  know,  all  the  fluids  and  many  of  the  solids  of  the 
body.     The  saliva  does  not  escape  the  general  contamination. 

'•  Bilious  saliva  chiefly  occurs  in  two  forms,  colored  and  color- 
less ;  more  rarely  it  is  met  with  containing  only  cholesterin. 

"  Colored  bilious  saliva  is  of  various  shades,  from  a  golden  yel- 
low to  a  deep  olive.  The  lighter  specimens  are  generally  alka. 
line,  the  darker  are  not  uncommonly  acid.     The  specific  gravity 


ON  THE  MORBID  CHANGES  OF  SALIVA. 


209 


of  this  saliva  is  greater  than  natural ;  its  smell  is  sickly  and 
offensive  ;  its  taste  bitter  and  nauseous ;  it  froths  easily  when 
agitated,  and  coagulates  abundantly  by  boiling ;  protracted 
ebullition  renders  it  ammoniacal,  and  deepens  its  hue  ;  it  contains 
only  a  minute  trace  of  ptyalin,  •which  usually  has  the  color  of 
the  original  fluid  ;  sulphocyanogen  is  generally  wanting ;  it 
exerts  scarcely  any  action  upon  starch ;  it  readily  becomes 
putrescent,  and  then  evolves  either  ammonia  or  its  hydrosul- 
phuret."* 

Wright  has  analyzed  it,  and  gives  the  following  as  the  contents 
of  a  single  specimen,  the  only  one,  apparently,  which  he  ex- 
amined : — 


Water  .... 

Ptyalin         .... 

Fatty  matter  and  fatty  acid  . 

Biliary  matter 

Cholesterin 

Albumen  with  soda  and  albuminate  of  soda 

Mucus  ...... 

Carbonates    C  Potassa  "^ 

Muriates      -<  Soda       V  .         ,         . 

Phosphates   I  Lime      J 

Loss     ....... 


986.7 
.5 
1.3 
3.2 
.4 
1.9 
1.6 

2.3 

2.1 

1000.0 


His  process  of  analysis  was,  first,  to  remove  the  ptyalin  and 
fat  by  ether,  then  to  exhaust  the  residue  with  boiling  alcohol. 
By  carefully  evaporating  and  crystallizing,  he  then  separated 
the  cholesterin  ;  he  then  extracted  the  biliary  matter,  leaving 
the  chlorides,  by  digesting  absolute  alcohol  upon  the  residue  of 
the  last  process. 

"  Colorless  bilious  saliva,  as  its  designation  is  intended  to 
signify,  is  free  from  any  appearance  of  intermixture  with  biliary 
matter.  Still,  it  is  never  so  transparent  as  the  natural  secretion, 
and  has   either  a  dead  white  or  a  slightly  dingy  aspect.     It  is 


14 


*  Wright,  op.  cit. 


210  THE  CHEMISTRY  OF  THE  MOUTH. 

sometimes  bitter,  but  more  frequently  imparts  a  mouldy  taste  to 
the  tongue.  It  is  always  alkaline,  with  an  abundance  both  of 
albumen  and  mucus.  Its  sulphocyanogen  is  deficient  though 
rarely  wanting ;  ptyalin  is  present  in  rather  less  proportion 
than  natural,  and  its  odor  is  not  recognizable  in  the  saliva, 
whether  cold  or  hot.  The  addition  of  nitric  or  muriatic  acid 
produces,  after  a  few  minutes  or  a  few  hours,  a  dull  yellow  color, 
which  gradually  deepens  to  a  faint  olive.  Protracted  boiling 
and  spontaneous  decomposition  give  rise  to  the  same  effect  in  an 
inferior  degree. 

"  This  saliva  will  convert  a  small  quantity  of  starch  into  gum, 
but  it  never  generates  any  sugar. 

"  Saliva  which  contains  cholesterin  free  from  intermixture 
with  biliary  matter,  is  of  rare  occurrence.  I  have  seen  it  only 
twice — in  one  instance  accompanying  dyspepsia  with  hepatic 
derangement,  and  in  the  other  succeeding  to  an  attack  of 
jaundice.  In  the  former  case,  it  lasted  for  three  or  four  days; 
in  the  latter  for  about  a  day  and  a  half.  The  quantity  secreted 
was  scarcely  more  than  ordinary,  but  my  attention  was  directed 
to  it  from  the  patients  complaining  of  a  greasy  taste  in  the 
mouth. 

"  This  saliva  is  white  and  shining,  and  more  dense  than  ordi- 
nary ;  it  has  an  alkaline  reaction,  does  not  redden  a  persalt  of 
iron,  and  is  nearly  odorless.  Its  albumen  is  in  excess,  but  its 
saline  constituents  are  in  small  proportion ;  it  possesses  feeble 
digestive  properties,  and  is  slow  of  decomposition." 

4 

BLOODY   SALIVA. 

This  is  a  rare  form  of  disease  and  one  of  no  great  consequence 
to  the  chemist,  however  important  it  may  be  to  the  practitioner 
of  medicine.  Its  color  depends  entirely  upon  the  condition  of 
the  haematin.  It  varies  from  a  brilliant  red  to  a  deep  brown  or 
black.  The  first  variety  is  darkened  by  the  various  gases  which 
similarly  affect  arterial  blood,  while  the  second  is  not  perceptibly 
brightened  by  oxygen.  Its  specific  gravity  is  greater  than  that 
of  the  healthy  secretions,  its  taste  bitter,  nauseous,  saline,  or 
insipid.     It  is  deficient  in  idtyalin^  but  usually  contains  the  nor- 


ON  THE  MORBID  CHANGES  OF  SALIVA.  211 

mal  quantity  of  sulphocyanogen.  It  is  darkened  by  decay,  and 
during  decomposition  evolves  ammonia.  It  absorbs  oxygen 
sparingly,  and  is  possessed  of  but  feeble  digestive  powers. 

ACID    SALIVA. 

The  acids  with  which  the  saliva  is  at  present  known  to  be  con- 
taminated are  the  acetic,  lactic,  hydrochloric,  oxalic,  and  uric.  It 
is  a  matter  of  great  practical  importance  to  ascertain  the  presence 
of  acid  in  the  saliva,  as  it  exerts  so  powerful  an  action  over  the 
teeth,  corroding  them  with  extreme  rapidity. 

Acid  saliva  may  have  a  sour  or  an  exaggerated  salivary  odor, 
both  of  which  are  increased  by  heat.  It  reddens  litmus-paper 
with  greater  or  less  intensity.  It  has  about  the  same  specific 
gravity  as  the  healthy  fluid,  and  sometimes  presents  an  opaque 
appearance,  from  the  coagulation  of  its  albumen.  Its  j^ty aim 
is  in  the  natural  proportion,  its  mucus  and  sulphocyanogen  com- 
monly in  excess. 

In  analysis,  the  acetic  and  hydrochloric  acids  may  be  separated 
from  the  salts  and  most  of  the  organic  matters,  by  careful  dis- 
tillation, and  then  neutralized  by  an  alkali,  evaporated  and  esti- 
mated from  the  salt.  Lactic  acid  is  estimated  in  the  ordinary 
process  of  analysis.  Some  of  it  may  be  left  on  the  filter.  This, 
with  pti/alin  and  fatty  acid,  is  removed  by  ether.  Water  sepa- 
rates it  with  the  ptyalin  from  the  fatty  acid,  and  the  acid  is  then 
precipitated  from  the  concentrated  aqueous  solution  by  acetate 
of  zinc.     Uric  acid  is  left  on  the  filter. 

Dr.  Wright  makes  a  distinction  between  the  secretion  ^ndi  the 
excretion  of  acid  by  the  salivary  glands,  attributing  the  former 
to  some  disturbance  of  the  glands  themselves  or  of  the  digestive 
apparatus,  the  latter  to  some  general  disorder  of  the  entire 
system. 

"  It  rarely  happens,''  says  he,  "  that  the  salivary  glands, 
when  in  a  state  of  healthy  activity,  perform  an  excernent  func- 
tion, to  free  the  blood  from  any  temporary  impurity,  unless  the 
organ  proper  for  this  task  shall  fail  in  discharging  it.  And 
then,  even  if  the  material,  oppressive  or  poisonous  to  the  blood, 
be  capable  of  being  neutralized  by  any  of  the  constituents  of  the 


212  THE  CHEMISTRY  OF  THE  MOUTH. 

saliva,  the  salivary  glands  are  rather  disposed  to  furnish  these 
constituents  in  increased  quantity  to  correct  the  offending  mat- 
ter, than  to  suffer  deterioration  or  suspension  of  their  charac- 
teristic function  in  becoming  partially  or  entirely  emunctories. 
This  rule,  however,  only  applies  to  the  sali/ary  apparatus  in  a 
healthy  condition ;  when  diseased  or  disordered,  spontaneously 
or  by  sympathy,  the  reverse  generally  happens." 

In  corroboration  of  this  opinion.  Dr.  Wright  cites  several  ex- 
periments, which,  indeed,  appear  to  be  conclusive.  He  found, 
on  injecting  various  acids  into  the  veins  of  healthy  dogs,  that 
an  immediate  and  great  increase  took  place  in  the  quantity  of 
the  secreted  saliva,  and  that  its  alhalinity  was  very  much  aug- 
mented. This  saliva  became  acid  in  one  case  just  before  death. 
In  one  instance  only  out  of  more  than  twenty  experiments,  did 
the  salivary  glands  excrete  the  injected  acid.  The  subject  of 
this  observation  was  a  strong  bull-terrier  dog,  into  the  veins  of 
which  had  been  thrown  three  drachms  of  pyroligneous  acid,  di- 
luted with  six  ounces  of  water.  At  first,  the  saliva  became  very 
frothy  and  alkaline,  and  continued  so  for  six  minutes,  at  the  ex- 
piration of  which  time  it  was  discharged  very  copiously,  and 
found  to  contain  acetic  acid.  The  ptyalism  continued  for  four 
hours,  and  it  was  not  until  seven  hours  had  elapsed  that  the 
saliva  had  resumed  its  normal  alkalinity. 

On  the  other  hand,  in  diseased  or  feeble  animals,  the  injected 
acids  were  usually  discharged  through  the  salivary  glands. 

Acidity  of  the  saliva  may  depend  upon  a  spontaneous  derange- 
ment of  the  secreting  glands.  This  is  usually  preceded  by  the 
ordinary  symptoms  of  increased  vascularity,  pain,  fulness,  tin- 
gling, &c.  It  may  be  intermittent  or  continued.  Stimulating 
gargarisms  have  commonly  the  effect  of  restoring  the  secretion 
to  its  normal  character  of  alkalinity.  It  may  also  depend  upon 
a  general  condition  of  acidity  in  the  system.  This  accompanies 
scrofula  and  other  cachexies,  and  depends  upon  a  variety  of  cir- 
cumstances which  Ave  cannot  at  present  consider. 

Disease  of  the  stomach  and  bowels  is  another  cause  of  acid 
saliva.  Donn^,  who  was  the  first  to  call  attention  to  this  patho- 
logical fact,  says  he  never  knew  a  single  instance  of  this  derange- 
ment in  the  salivary  secretion,  in  which  the   functions  of  the 


ON  THE  MORBID  CHANGES  OF  SALIVA.  213 

stomach  were  healthily  performed.  This  state  of  the  saliva  may 
be  absent  in  some  functional  disorders  of  the  alimentary  canal, 
but  is  always  present  in  inflammation  of  that  important  tract. 

"I  have  never  seen,"  says  Dr.  Wright,  "a  case  of  gastro- 
enteritis, whether  in  a  severe  or  a  mild  form,  in  which  the  saliva 
was  not  acid ;  and  I  have  remarked  that  one  of  the  first  and 
most  favorable  indications  of  recovery  is  the  return  of  the  saliva 
to  a  neutral  or  alkaline  state.  I  have  known  a  patient  to  suffer 
for  days  from  an  attack  of  mild  gastro-enteritis,  and  his  saliva 
to  be  strongly  acid,  without  his  consciousness  of  it,  and  yet  a 
sudden  aggravation  of  his  gastric  symptoms  to  render  the  saliva 
almost  immediately  intolerable  from  its  extreme  acidity.  On 
the  other  hand,  I  have  heard  a  patient  who  complained  not  less 
of  the  excoriation  and  smarting  in  his  mouth  than  of  the  burning 
heat  and  pain  in  his  stomach,  declare  the  acidity  and  acid  taste 
of  his  saliva  to  be  gone  in  a  few  minutes  after  the  application  of 
leeches  to  his  epigastrium.  The  same  effect  is  frequently  pro- 
duced by  the  counter-irritation  of  sinapisms  and  blisters.  Nay, 
I  have  known  the  saliva  of  a  gastro-enteritic  patient  to  have  a 
strongly  acid  reaction  before  the  application  of  a  blister  to  the 
epigastrium,  and  to  be  equally  strong  in  its  alkalinity  during  the 
time  such  blister  was  in  operation. 

"  The  saliva  is  impregnated  with  lactic  acid  chiefly  in  gout, 
rheumatism,  ague,  diabetes,  and  gastro-enteritis ;  with  acetic  acid 
in  aphthffi,  scrofula,  scorbutus,  smallpox,  protracted  indigestion, 
and  after  the  use  of  acescent  wines;  with  muriatic  acid  in  simple 
gastric  derangement  from  immoderate  or  improper  animal  food, 
and  with  uric  acid  in  gouty  affections.  When  oxalic  acid  exists 
in  the  saliva,  its  presence  will  most  likely  be  dependent  upon 
depraved  digestion  or  imperfect  assimilation. 

"Acidity  of  the  saliva  is  apt  to  occur  in  various  other  general 
and  local  disorders,  particularly  in  fevers,  both  of  the  typhoid 
and  inflammatory  types  ;  in  measles,  prior  to  the  eruption,  and 
often  subsequently  ;  in  miliary  fever,  when  the  acidity  is  some- 
times so  excessive  as  to  corrode  the  gums  and  impart  a  sensible 
roughness  to  the  teeth ;  in  maniacal  cases,  during  the  exacerba- 
tions of  which  the  acid  impregnation  is  often  remarkably  in- 
creased ;  in  phthisis,  in  protracted  venereal  disease,  in  many 


214  THE  CHEMISTRY  OF  THE  MOUTH. 

skin  diseases,  in  amenorrhoea,  rickets,  catarrhs,  mumps,  quinsy, 
cancer  affecting  any  part  of  the  digestive  apparatus,  worms,  and 
in  the  tedious  dentition  of  weakly  or  scrofulous  children." 

ALKALINE    SALIVA. 

This  variety,  dependent  on  excess  of  soda,  differs  little  in  ex- 
ternal character  from  healthy  saliva.  It  has  a  mucous  smell, 
and  does  not  give  the  red  tint  with  iron,  till  after  neutralization 
with  an  acid.  It  contains  excess  of  albumen,  and  when  the 
alkali  is  greatly  superabundant,  a  deficiency  of  ptyalin  and  sul- 
phocyanogen.  It  acts  less  powerfully  on  starch  than  the  healthy 
fluid,  decomposes  readily,  and  becomes  mouldy  and  ammoniacal. 

It  is  possible  that  this  condition  of  the  saliva  may  accompany 
an  excess  of  carbonate  of  soda  administered  medicinally.  It 
certainly  attends  the  injection  of  this  salt  into  the  veins.  It  is 
remarkable,  however,  that  soda,  the  alkali  peculiar  to  saliva,  is 
alone  eliminated  through  the  salivary  secretion,  the  other  alkalies 
and  alkaline  earths  never  being  found  in  it,  but  always  being 
discharged  through  the  common  emunctories.  Experiments  with 
mixed  carbonate  of  soda  and  carbonate  of  potash  were  very  in- 
structive. The  saliva  and  urine  both  became  alkaline,  but  the 
former  contained  the  soda,  the  latter  the  potash. 

Neuralgia  and  nervous  disturbance  generally  have  a  remark- 
able connection  with  alkalinity  of  the  saliva.  In  neuralgia, 
nervous  toothache,  and  earache,  this  alkalinity  is  observable, 
especially  on  the  affected  side.  Nervous  disorder  of  the  stomach, 
liver,  and  other  remote  organs  are  also  subject  to  the  same  law. 
Epilepsy  is  also  accompanied  by  alkaline  saliva,  in  some  instances, 
so  decided  as  to  impart  an  unpleasant  taste  to  this  liquid.  In 
hysteria,  the  discharge  sometimes  amounts  to  ptyalism ;  it  is  of 
a  low  specifi.c  gravity,  limpid,  and  feebly  alkaline.  "In  the  ex- 
citement or  exacerbation  of  mania,  the  saliva  is  frequently  in  a 
state  of  morbid  alkalinity.  The  secretion  itself  may  be  either 
lavish  or  limited.  I  once  saw  the  fury  of  a  madman  almost  in- 
stantly subdued  by  the  sudden  occasion  of  a  profuse  ptyalism, 
which  continued  for  nearly  three  hours.  The  fluid  was  very 
strongly  alkaline.     In  many  cases  of  mania,  the  saliva  is  re- 


ON  THE  MORBID  CHANGES  OF  SALIVA.  215 

markable  for  its  acidity.  Its  continued  secretion  excoriates  the 
lips  and  gums,  and  has  been  known  even  to  corrode  the  teeth. 
In  such  instances,  there  can  be  little  doubt  that  the  function  of 
the  stomach  is  considerably  deranged."* 

Ammoniacal  saliva  is  rare.  It  is  dingy  and  clouded,  with  a 
very  strong  alkaline  reaction.  The  odor  is  ammoniacal  or  dis- 
agreeably mucous.  Fixed  alkali,  sulphocyanogen,  and  ptT/alin 
are  all  wanting.  It  possesses  no  digestive  property.  The 
alkalinity  is  dissipated  by  heat,  on  account  of  the  volatilization 
of  the  ammonia.  It  is  secreted  in  less  quantity  than  usual,  and 
is  excessively  offensive  to  the  taste.  It  it  dijSicult  to  swallow, 
and  clings  to  the  mucous  membrane  of  the  mouth. 

It  indicates  a  cachectic  state  of  the  system.  Wright  saw  it 
in  putrid  fever,  in  scurvy,  and  in  purpura  hemorrhagica. 

CALCAREOUS  SALIVA. 

The  normal  proportion  of  phosphate  of  lime  is  about  .6  parts 
in  every  1,000  of  saliva.  This  proportion  may  be  morbidly  in- 
creased, and  then  carbonate  of  lime  is  also  present.  Saliva 
containing  this  abundance  of  calcareous  matter,  deposits  it  either 
on  the  teeth,  or  in  the  excretory  ducts  of  the  different  salivary 
glands. 

This  variety  of  saliva  is  usually  opaque,  slightly  frothy,  and 
white,  like  milk.  Through  the  microscope  it  looks  curdy.  When 
the  proportion  of  lime  is  considerable,  the  fluid,  after  standing, 
deposits  a  copious  precipitate,  leaving  the  supernatant  liquid 
clear.     It  may  be  acid,  alkaline,  or  neutral. 

In  a  case  of  mollities  ossium,  Dr.  Wright  found  1.4  per  cent, 
of  phosphate  of  lime  in  the  saliva. 

SALINE  SALIVA. 

The  quantity  of  salts  contained  in  saliva  is  small  but  constant, 
two  of  them  only  being  subject  to  variation.  These  are  sulpho- 
cyanide  of  potassium  which  is  liable  to  diminution,  and  chloride 
of  sodium,  which  may  be  increased. 

Excess  of  this  salt  in  the  saliva  may  depend  upon  an  increase 

*  Wright,  op.  cit. 


216  THE  CHEMISTRY  OF  THE  MOUTH. 

of  the  natural  amount  present  in  the  blood.  Injection  of  chlo- 
ride of  sodium  into  the  veins  of  an  animal  always  produces  this 
condition  of  the  salivary  secretion.  Persons  who  eat  much  salt 
are  subject  to  an  increase  of  this  constituent  in  the  saliva.  If 
much  liquid  is  taken,  the  salt  is  eliminated  through  the  skin,  and 
in  some  persons  whose  cutaneous  transpiration  is  very  active,  it 
passes  off  with  great  rapidity  by  this  outlet.  Men  working  in 
salt  mines  and  manufactories  are  often  covered,  on  the  surface 
of  their  bodies,  and  especially  their  foreheads,  with  crystals  of 
this  salt  which  has  transuded.  Dr.  Wright  says  that  he  once 
examined  the  men  in  a  large  salt  warehouse,  and  found  that 
those  whose  skin  was  impermeable  to  the  saline  particles,  suffered 
from  a  constant  salt  taste  in  their  mouths,  and  their  saliva  was 
impregnated  with  chloride  of  sodium ;  while  those  whose  skins 
allowed  a  ready  transit  to  the  salt,  were  rarely  troubled  with 
saline  saliva,  or  with  thirst. 

It  may  also  be  produced  by  a  purely  local  and  idiopathic  dis- 
order of  the  salivary  glands.  Functional  disturbance  of  the 
digestive  apparatus,  too,  produces  it. 

PURIFORM    SALIVA. 

This  is  nothing  but  saliva  with  an  admixture  of  pus,  and  is, 
of  course,  to  be  recognized  as  purulent  discharges  always  are. 
These  need  no  allusion  to  them  in  this  place.  We  shall  only 
say  that  it  has  a  greater  specific  gravity  and  more  albumen  than 
normal  saliva;  that  it  is  always  alkaline;  seldom  deficient  in  the 
characteristic  elements  of  the  natural  secretion ;  and  that  it  is 
easy  of  decomposition,  and  feeble  in  its  digestive  action. 

FETID    SALIVA. 

Various  strongly  scented  substances  taken  into  the  system, 
either  at  the  mouth,  or  by  cutaneous  absorption,  may  be  ab- 
sorbed by  the  salivary  glands,  and  communicate  their  peculiar 
odor  to  the  saliva.  The  term  fetid  saliva,  however,  is  not  ap- 
plicable to  these  conditions  of  the  secretion,  but  to  a  morbid 
alteration  of  its  constitution,  which  may  depend  upon  either  local 
or  general  disturbance. 


ON  THE  MORBID  CHANGES  OF  SALIVA.  217 

This  variety  of  saliva,  according  to  Wright,  is  always  turbid 
and  flocculent ;  variable  in  color,  but  usually  of  a  red,  brown, 
green,  or  yellow  hue  ;  exhaling  a  putrid  or  cheesy  odor  ;  greasy 
and  sticky  to  the  touch;  deficient  in  ptyalin  and  sulphocyanogen ; 
either  acid  or  alkaline  ;  having  little  affinity  for  oxygen,  and 
scarcely  any  digestive  properties.  Its  color  and  smell  are  due 
to  fatty  matter,  which  is  separated  by  ether  or  boiling  alcohol. 
Tiedemann  and  Gmelin  suggest,  that  some  phosphorus  they 
found  combined  with  this  fat  may  communicate  the  unpleasant 
odor  to  it.  Wright,  however,  was  unable  to  find  uncombined 
phosphorus  in  the  saliva.  It  can  hardly  be  necessary  to  add 
that  this  fluid  not  only  does  not  assist,  but,  by  its  nauseous 
properties,  absolutely  impedes  the  function  of  digestion, 

ACRID    SALIVA. 

No  fact  is  better  known  than  that  serious  morbid  changes  may 
take  place  without  any  discoverable  alteration,  anatomical  or 
chemical,  in  the  solids  or  fluids  of  the  body.  So,  too,  saliva 
may  be  gravely  disturbed  without  any  discernible  chemical 
chantre.  The  saliva  of  maniacs  is  often  so  acrid  as  to  excoriate 
those  parts  of  the  body  with  which  it  comes  in  contact,  and  yet 
analysis  reveals  the  natural  constituents  in  their  due  proportion. 
Dr.  Wright  thinks  this  saliva  capable  of  communicating  hydro- 
phobia. One  thing  is  certain,  bites  of  animals,  and  even  of 
men,  inflicted  in  fits  of  furious  passion,  have  produced  this  ter- 
rible malady.  If  we  consider,  also,  that  the  most  careful  ex- 
amination of  hydrophobic  saliva  has  failed  to  reveal  any  altera- 
tion in  the  chemical  composition  of  this  fluid,  we  shall  have  but 
little  difficulty  in  arriving  at  the  same  conclusion  with  Dr. 
Wright ;  that  the  saliva,  thus  unnaturally  active,  diff'ers  from  the 
healthy  fluid  only  in  possessing,  in  an  extraordinary  degree, 
those  properties  which  are  peculiar  to  it. 

Of  COLORED  SALIVA,  it  is  not  neccssary  to  speak  at  any  length. 
Indigo  and  some  other  coloring  matters  are  capable  of  tinging 
this  fluid.  Acetate  of  lead  imparts  to  it  a  distinct  bluish  tint. 
In  the  advanced  stages  of  fever,  and  in  purpura,  the  saliva  is 
often  darkly  blue.     Dr.  Wright  suspects  this  to  be  due  to  Prus- 


218 


THE  CHEMISTRY  OP  THE  MOUTH. 


sian  blue,  formed  in  consequence  of  the  decomposition  of  the 
blood. 

Frothy  Saliva  does  not  differ  from  the  healthy  fluid  in 
chemical  composition.  Its  only  peculiarities  are  its  appearance, 
and  its  undue  viscidity.  It  is  pathognomonic  of  nervous  excite- 
ment, being  found  in  hydrophobia,  epilepsy,  &c. 


URINARY  SALIVA. 

Dr.  Prout  records  a  case  in  which,  the  urine  being  greatly 
diminished,  ptyalism  came  on.  The  saliva  had  a  urinous  taste 
and  an  alkaline  reaction;  "was  opalescent,  slightly  ropy,  and 
foamed  when  agitated.  Its  specific  gravity  was  1.0055.  The 
soluble  salts  of  lead,  mercury,  and  silver,  and  the  mineral  acids 
produced  precipitates  in  it.  Dilute  acetic  acid  caused  a  preci- 
pitate, but  none  could  be  obtained  afterwards  by  the  addition  of 
ferrocyanide  of  potassium,  showing  the  absence  of  albumen.  The 
analysis  of  Dr.  Prout  yielded  the  following  results : — 


Water 

Animal  matter  peculiar  to  saliva       .         .         .         . 
Alcoholic  extract,  apparently  similar  to  that  obtained 

from  the  blood  .... 
Sulphuric  acid  .... 

Hydrochloric  acid  .... 
Phosphoric  acid  .... 
Alkali,  partly  potash  and  partly  soda 


991.35 
3.33 

1.06 
.90 
.75 
.06 

2.55 

1000.00 


"  The  urine  of  this  woman  was  of  an  amber  color,  and  slightly 
opaque.  Its  specific  gravity  was  1.0131.  It  contained  crystals 
of  uric  acid,  and  reddened  litmus  paper  more  strongly,  than  usual. 
It  contained  much  less  urea  than  natural,  but  a  large  proportion 
of  a  brown  animal  substance,  which  appeared  to  render  it  very 
prone  to  decomposition,  especially  when  exposed  to  heat.  With 
a  view  of  increasing  the  flow  of  urine,  diuretics  were  given. 
These  produced  the  desired  effect.  The  urine  was  rendered 
more  copious  and  natural,  while  the  salivary  discharge  was  pro- 


'  \ 


ON  THE  MORBID  CHAXGES  OF  SALIVA.  219 

portionally  dimlnislied."  The  saliva  here  was  evidently  vica- 
rious- 

Dr.  Wright  records  a  case  of  granular  degeneration  of  the 
kidneys,  in  which,  on  the  suspension  of  the  urinary  secretion, 
vicarious  ptyalism  set  in,  to  an  amount  varying  from  a  pint  and 
a  half  to  two  pints  and  a  quarter  in  the  twenty-four  hours.  "  The 
secretion  was  of  a  fawn  color,  viscid,  and  loaded  with  films  and 
nebulas,  which  finally  settled  into  a  heavy,  opaque  deposit.  Its 
odor,  at  first  putrid,  became  ammoniacal  in  a  few  hours,  and  the 
patient  complained  that  its  taste  was  salty  and  urinous.  It  was 
not  reddened  by  a  persalt  of  iron,  and  it  furnished  not  a  trace 
oi  ptyalin.  An  alcoholic  extract  of  its  dried  residue  was  mode- 
rately diluted  and  treated  with  nitric  acid,  when  crystals  of 
nitrate  of  urea  were  immediately  deposited.  The  proportion  of 
urea  never  exceeded  5  per  cent. ;  but,  until  the  kidneys  resumed 
their  function,  neither  the  salivation  was  diminished  nor  was  the 
saliva  free  from  the  presence  of  urea.  Directly,  however,  that 
the  usual  reaction  was  re-established,  the  action  of  the  salivary 
glands,  and  their  product,  became  perfectly  healthy." 

Dr.  "VYright  also  records  a  case  of  ascites,  arising  from  sub- 
acute peritonitis,  in  which  urea  was  detected  in  the  saliva.  The 
saliva  was  of  a  pale  chocolate  color,  slightly  ammoniacal  in  odor, 
alkaline  in  reaction,  and  disagreeable  in  taste.  The  quantity 
discharged  in  twenty-four  hours  was  fourteen  ounces  and  a  half. 
No  urine  was  secreted  for  three  days  after  the  ptyalism  occurred. 
From  a  pint  and  a  half  of  this  saliva,  ten  grains  of  urea  were 
obtained  by  the  usual  methods. 

GELATINOUS  SALIVA. 

Gelatinous  saliva  somewhat  resembles  gum  water  in  appear- 
ance ;  it  is  imperfectly  transparent  and  somewhat  dingy,  viscid, 
and  tremulous  when  cold,  but  becoming  more  fluid  and  clear  on 
the  application  of  heat.  It  does  not  easily  froth  when  agitated, 
decomposes  easily  and  becomes  mouldy  and  sour.  Its  taste  is 
mawkish,  and  its  smell  greasy ;  its  sulphocyanogen  and  ptyalin 
diminished  in  quantity,  its  specific  gravity  varying  from  1.0099 
to  1.0101.     Its  reaction  is  neutral  or  faintly  acid,  absorbs  oxy- 


220 


THE  CHEMISTRY  OF  THE  MOUTH. 


gen  sparingly,  and  possesses  little  or  no  digestive  power.     It 
occurs  in  a  debilitated  and  depraved  state  of  the  system. 

Dr.  Wright's  analysis  reveals  the  following  as  its  constitu- 
tion:— 


Water         ...... 

Ptyalin      ...... 

Fatty  acid  ..... 

Gelatine     ...... 

x^lbumen  with  soda  and  albuminate  of  soda 
Sulphocyanide    ..... 

Mucus         ...... 

Lactates      ^    r  Potash  ^ 

Muriates      I  I  Soda     I      .         .         . 

Phosphates)    (Lime    J 

Loss  ....... 


987.2 

.6 

.8 

3.6 

1.3 

trace. 

2.5 

1.7 


1000.0 


MILKY  SALIVA. 


This  form  of  saliva  is  a  metastasis  from  the  mammary  glands, 
and  may  take  place  either  at  the  commencement  of  arrest  of  this 
secretion,  or  at  its  close  as  a  critical  flux. 

It  is  an  opaque  white  fluid,  sometimes  uniform  in  appearance, 
but  often  curdy.  Acetic  acid  increases  the  coagula.  The  se- 
cretion is  healthy,  except  with  the  addition  of  the  constituents 
of  milk.  Its  specific  gravity  is  high,  reaching,  according  to 
Wright,  1.0125.  It  is  faintly  alkaline  or  neutral,  and  is  easily 
decomposed.  It  readily  absorbs  oxygen,  but  possesses  very 
feeble  digestive  properties. 


CHANGES  OF  THE  SALIVA  IN  DISEASE. 

We  have  but  little  to  add  to  what  has  already  been  said  upon 
this  subject.  We  have  already  noticed  the  acidity  of  this  fluid 
in  certain  inflammatory  affections  and  functional  disturbances  of 
the  alimentary  canal.  Another  peculiarity  of  the  saliva  in  inflam- 
matory diseases  is  a  diminution  of  the  normal  quantity  of  water. 


ON  THE  MORBID  CHANGES  OF  SALIVA.  221 

as  may  be  seen  from  the  following  mean  of  six  analyses  made  on 
the  saliva  in  cases  of  inflammatory  fever,  pneumonia,  and  erysi- 
pelas. For  facility  of  comparison,  the  table  of  healthy  saliva 
constructed  by  L'Heritier,  an  average  of  ten  analyses,  is  placed 
beside  this  result : — 

In  inflammation.  In  health. 

Water         .         .         .     968.9  986.5 

Organic  matter  .       30.0  12.6 

Inorganic  matter         .         1.1  .9 

The  proportion  of  ptyalin  was  found  to  be  increased. 
In  chlorosis,  saliva  suffers  from  watery  degeneration,  in  the 
same  manner  as  the  animal  tissues  and  secretions  generally.     In 
dropsy  with  albuminous  urine,  the  saliva  was  found  by  L'Heritier 
to  contain  : — 

Water 985.9 

Organic  matter        ....       13.6 
Inorganic  matter     .         .         .         .  .5 

Scherer  has  published  an  analysis  of  the  saliva  of  a  girl  of 
fifteen  years  of  age,  who  labored  under  a  scorbutic  disease  of  the 
mouth.  There  was  copious  ptyalism,  the  discharge  from  the 
mouth  amounting  to  forty  ounces  in  twenty-four  hours.  The 
secretion  was  very  liquid,  fetid,  and  alkaline.  Its  specific  gra- 
vity was  1004. 

The  following  is  the  result  of  the  examination  of  this  fluid : — 

Water 988.8 

Solid  constituents — 

A  caseous-like  substance  precipitable  by  acetic  acid  6.5 

Fat  taken  up  by  ether  .....    0.6 


Extractive  matter  and  ptyalin 
Carbonate  of  soda 
Chloride  of  sodium 
Phosphate  of  lime 


1.8 
1.2 
O.T 
0.4 


11.2 


1000.0 


On  examination  with  the  microscope  immediately  after  its  dis- 
charge, the  fluid  was  found  to  contain  a  large  number  of  infusoria 
and  confervoid  growths. 


222  THE  CHEMISTRY  OF  THE  MOUTH. 


CHAPTER   IV. 

MUCUS. 

The  ■whole  body  is  inclosed  in  one  vast  tegumentary  mem- 
brane, the  internal  surface  of  Trhich  differs  widely  from  the  ex- 
ternal. This  internal  surface  has  been  called  mucous  menibrane  ; 
it  is  covered  with  epithelium,  and  kept  moist  by  a  secretion  con- 
stantly flowing  over  it,  which  has  been  called  mucus.  It  must 
be  confessed,  however,  that  this  term  mucus  has  been  very  irre- 
gularly applied,  and  that  many  other  portions  of  the  body  may 
contain  viscid  fluids  not  distinguishable  from  true  mucous  juice. 
The  difficulties  of  investigation  are  very  great;  for,  independ- 
ently of  this  primary  one,  the  mucous  secretion  is  so  small  in 

quantity  and  so  mixed  up  with 
^ig-  22.  other  heterogeneous  fluids,  that 

i    I     *^  ^  )  it  is  almost  impossible  to  get  at 

.        ,  \    * ,  -i-      \,<,        any  definite  facts  in  reference  to 
I      _\ '  \\p}_  Q  ^  ',©■         it.     It  is  well  known  that,  dur- 
*^    '"''^y  V'i:':  ^'^'X^^o.''  ''''J'\        i^g  health,  the  secretion  of  the 
(g     ^^      »'' "^vU/?"-^'*®       mucous     membranes     is     very 
(?      '.'• .  o  'cHt  A' ) '       scanty,  and  that  it  is  only  dur- 
(O       iJ^'*"'      *M    tS^-c      ^      ing  disease  that  any  quantity  of 
^^  A  -.S^ fs.'*'  \\^^r'^'^  '        *^®   so-called  mucous  secretion 
"-^  i.^JC        ■       accumulates.     It  would  be  con- 

jiucus.  "^  trary  to  all  scientific  propriety 

to  consider  this  increased  secre- 
tion physiological,  and  to  reason  from  it  on  the  properties  of 
normal  mucus.  Vogel  has  found  that,  under  these  circumstances, 
the  mucous  membranes  throw  off  more  corpuscles,  and  also  se- 
crete an  albuminous  coagulable  matter  not  present  in  the  normal 
secretion.  These  circumstances  are  mentioned  to  show  the  diffi- 
culty attending  the  investigation  of  the  chemistry  of  this  secre- 
tion. 


MUCUS.  223 

Normal  mucus  is  denser  than  water,  and  when  not  buoyed  up 
by  globules  of  air,  sinks  gradually  in  that  fluid.  When  dried, 
or  even  when  only  inspissated,  as  in  some  cases  of  slight  irrita- 
tion of  the  bronchi  giving  rise  to  morning  cough,  it  sinks  very 
rapidly  in  water.  It  seems  to  con- 
sist almost  entirely  of  epithelium  ^'^*  ^^• 
scales  held  together  by  a  pellucid 
juice.  These  scales  vary,  of  course, 
in  their  appearance,  with  the  source 
whence  they  are  derived. 

Besides  epithelium  scales,  mucus 
contains  globules  or  corpuscles,  which 
cannot  be  satisfactorily  distinguished  „     ,  ,  , 

_•'  o  Pus-globules. 

from  those  of  pus,  either  by  micro- 
scopical or  micro- chemical  characters.  It  requires  the  aid  of 
water  or  of  acetic  acid  to  bring  into  view  the  nuclei  of  the 
mucus-corpuscles,  which  then  present  one  or  two  fissures.  In 
the  diseases  known  as  diphtheritic  inflammations,  fibrinous 
coagida,  taking  the  form  of  the  tube  from  which  they  are  thrown 
off,  are  found,  in  addition  to  the  elements  already  enumerated  as 
present  in  the  exudation  from  these  membranes.  After  these 
inflammations  have  subsided,  infiammatory  globules  or  granular 
cells  make  their  appearance.  They  are  also  found  in  certain 
inflammations  of  the  mucous  membrane  which  are  not  diph- 
theritic. The  gray  color  of  such  sputa  is  supposed  by  Lehmann 
to  depend  upon  the  irregular  refraction  of  light  among  the  nu- 
merous highly  refracting  cells.  The  usual  method  of  explaining 
the  phenomenon  is  to  attribute  it  to  the  soot  and  fine  carbonace- 
ous particles  constantly  inhaled,  more  particularly  by  the  inha- 
bitants of  large  cities,  and  by  certain  classes  of  workmen. 

Besides  the  morphological  elements,  we  find  in  muQU^,  fat-cells, 
molecular  or  elementary  granules,  various  cellular  formations, 
and  only  occasionally  vihriones  and  microscojncal  fungoid 
groivths. 

The  liquid  portion  of  mucus,  according  to  Simon,  invariably 
exhibits  an  alkaline  reaction.  This  statement,  however,  must 
be  taken  with  allowances.  It  is  always  difficult  to  obtain  mucus 
unmixed  with  other  secretions,  so  that  a  source  of  fallacy  is 


224  THE  CHEMISTRY  OF  THE  MOUTH. 

here  introduced  which  cannot  always  be  guarded  against.  We 
have  already  mentioned  that  Marshall  and  Garrod,  on  investi- 
gating this  point,  in  the  mucus  secreted  by  the  membranes  of 
the  mouth  in  the  foetal  state,  found  the  reaction  invariably 
alkaline.  Andral,  moreover,  maintains  that  perfectly  pure 
mucus  is  always  acid  in  a  normal  state.  Such  an  assertion,  as 
Lehmann  observes,  is  not  easily  proved,  since  we  are  unac- 
quainted with  any  entirely  pure  mucus.  That  there  are  /ree 
acids  in  the  mucus,  every  chemist  knows.  They  are  included 
among  extractive  matters.  Nothing,  however,  is  positively 
known  in  regard  to  this  free  acid,  which  occurs,  among  other 
instances,  in  the  mucus  of  the  mouth,  and  of  the  bladder. 

When  water  is  added  to  the  clear  mucous  fluid,  a  turbidity  is 
visible,  which  gradually  forms  itself  into  a  finely  granular  pre- 
cipitate. This  is  the  characteristic  chemical  constituent  of 
mucus,  from  which  it  has  received  the  name  of  mucin. 

This  substance  is,  however,  not  invariably  insoluble  in  water, 
for  Scherer  has  described  a  mucus  soluble  in  water,  and  separa- 
ble from  the  morphological  constituents  by  filtration.  The  solu- 
tion of  mucin  does  not  coagulate  on  the  application  of  heat,  but 
in  some  instances  becomes  more  fluid,  and  more  like  a  true  so- 
lution. Alcohol  precipitates  it  in  flakes  and  threads.  Dilute 
acetic  acid  precipitates  it  in  viscid  flakes,  which  are  sometimes 
strong  enough  to  admit  of  traction.  This  precipitate  is  insolu- 
ble in  dilute  acetic  acid,  but,  in  the  concentrated  acid,  they  dis- 
solve with  the  aid  of  heat.  The  mineral  acids,  in  like  manner, 
precipitate  the  mucin  when  dilute,  and  dissolve  it  again,  when 
concentrated.  On  the  other  hand,  it  dissolves  very  readily  in 
dilute  alkalies,  but  much  less  speedily  in  concentrated  solutions. 
Acetic  acid  precipitates  much  less  mucin  from  concentrated  than 
from  dilute  alkaline  solutions,  because  mucin,  if  not  altogether 
soluble,  forms  at  least  a  gelatinous  fluid  with  moderately  strong 
alkaline  solutions.  In  these  cases,  acetate  of  potash  prevents 
the  mucin  from  separating  perfectly  in  flakes.  Gelatinous  mu- 
cus is  often  coagulated  by  water,  so  that  it  loses  its  translucent, 
gelatinous  character,  and  becomes  denser.  Simon  supposes  that 
the  mucin  is  held  in  solution  by  an  alkali,  and  that  the  abstrac- 
tion of  this  by  water  causes  the  change.     Ferrocyanide  of  po- 


MUCUS.  225 

tassium  yields  no  precipitate  with  mucin,  whether  in  acid  or  in 
alkaline  solution,  unless  albumen  or  some  other  protein  body  be 
present.  Mucus,  however,  which  is  boiled  with  concentrated 
acetic  acid,  forms  an  exception  to  this  rule,  being  copiously  pre- 
cipitated by  ferrocyanide  of  potassium.  Concentrated  nitric 
acid  colors  it  yellow,  and  hydrochloric  acid,  with  the  aid  of 
heat  and  atmospheric  exposure,  turns  it  blue.  Tannic  acid  or 
basic  acetate  of  lead  gives  a  copious  precipitate  with  a  weak 
alkaline  solution  of  mucin,  while  alum,  chromic  acid,  corrosive 
sublimate,  neutral  acetate  of  lead,  and  other  metallic  salts,  only 
produce  a  slight  turbidity. 

Pyin^  described  by  Giiterbock  as  a  constituent  of  pus,  was 
supposed,  by  Eichholtz  and  others,  to  be  identical  with  mucin ; 
but  a  comparison  of  the  reactions  of  pyin  found  in  pure  pus, 
with  those  of  mucin,  will  show  that  this  opinion  is  erroneous. 

According  to  Lehmann,  most  of  the  elementary  analyses  of 
mucus  which  have  been  made,  afford  us  scarcely  any  aid  in 
judging  of  the  composition  of  mucin,  because  the  epithelium 
could  not  be  separated  from  it.  Scherer,  however,  obtained, 
from  what  was  probably  an  enlarged  hursa  muco8a  between  the 
trachea  and  the  oesophagus,  a  mucus  which  he  could  filter  from 
the  structural  components  of  the  fluid.  He  precipitated  the 
mucin  from  thie  solution  by  means  of  alcohol,  and  then  boiled  it 
repeatedly  with  alcohol  and  ether.     Thus  purified  it  gave  : — 

Carbon      .......  52.10 

Hydrogen          .         .         .         .         .         .  6.97 

Nitrogen  .         .         ._       .         .         .        '.  12.82 

Oxygen     .         .         .'       .         .         .         .  28.11 


100.00 


No  sulphur  was  found  in  it,  but  4.114g  of  white  ash  was 
obtained  from  it,  which  contained  alkaline  carbonates,  and  a 
tolerably  large  quantity  of  phosphate  of  lime. 


15 


226 


THE  CHEMlSTKY  OF  THE  MOUTH. 


We  subjoin  an  analysis  of  normal  nasal  mucus  by  Berzelius: — 


Water 

Mucin       ....... 

Alcohol-extract  and  alkaline  lactates  . 
Chlorides  of  sodium  and  potassium 
Water-extract,  with  traces  of  albumen  and 
phosphates     ...... 

Soda,  combined  with  mucus 


930.7 

53.3 

3.0 

5.6 

3.5 
3.9 

1000.0 


Nasse  has  made  a  very  elaborate  analysis  of  the  pulmonary 
mucus  expectorated  in  the  morning  by  a  healthy  man.  No.  1 
refers  to  the  mucus  itself,  and  No.  2  to  the  solid  residue : — 


No.  1. 

No.  2. 

Water      . 

955.520 

Solid  constituents     . 

44.480 

Mucin,  with  a  little 

albumen 

23.754 

53.405 

Water-extract     . 

8.006 

18.000 

Alcohol-extract  . 

1.810 

4.070 

Fat    . 

2.887 

6.490 

Chloride  of  sodium 

5.825 

13.095 

Sulphate  of  soda 

0.400 

0.880 

Carbonate  of  soda 

0.198 

0.465 

Phosphate  of  soda 

0.080 

0.180 

Phosphate  of  potash, 

with  traces  of  iron 

0.974 

2.190 

Carbonate  of  potash 

0.291 

0.655 

Silica  and  sulphate 

of  potash 

• 

0.255 

0.570 

1000.00      44.480      100.000 
Jacubowitsch  has  published  the  following  analysis  of  buccal 


mucus : — 


MUCUS.  227 

Water 990.02 

Solid  matters : — 

Organic  matter  soluble  in  alcohol         1.67 
"  "       insoluble      "  2.18 

Fixed  salts         ....        6.13  9.98 


1000.00 


The  aqueous  and  alcoholic  extracts  of  mucus  have  not  been 
very  carefully  examined.  Their  quantity  is  no  doubt  increased 
by  the  secretions  of  the  glands,  which  are  imbedded  in  the 
mucous  membrane.  From  this  secretion,  the  true  mucus  must 
be  carefully  distinguished.  The  intestinal  juice,  already  de- 
scribed, must  not  be  confounded  with  mucus.  It  is  a  glandular 
product. 

In  commenting  upon  the  various  analyses  of  mucus,  Lehmann 
observes : — 

"  Unfortunately,  no  attention  has  been  paid,  in  these  analyses 
of  the  normal  mucus,  to  the  relation  existing  between  the  potash 
and  the  soda.  Yet  the  establishment  of  this  relation  is  not 
devoid  of  importance  in  the  solution  of  the  question,  whether 
the  blood-corpuscles  take  part  in  the  preparation  of  the  mucus 
as  they  do  in  that  of  most  other  secretions ;  or  whether  the 
mucus  is  formed  solely  from  the  constituents  of  the  blood- 
plasma  ?  I  know  of  only  one  analysis  of  the  kind  suited  to 
throw  light  on  the  subject,  and  this  yielded  more  potash  and 
less  soda  in  the  ash  of  the  mucus  than  in  that  of  the  blood- 
serum  ;  but  as  this  mucus  had  been  secreted  during  an  acute 
catarrh,  and  besides  being  very  rich  in  young  cells  (mucus-cor- 
puscles), contained  also  some  granular  cells,  it  does  not  afford 
any  conclusive  evidence." 

In  inflammation,  or  catarrhal  inflammation  of  mucous  surfaces, 
the  mucus  secreted  contains  a  varying  quantity  of  albumen. 
Normal  mucus  may  also  contain  albumen.  This  is  always  the 
case  in  the  mucus  of  the  stomach,  which  is  intermixed  with  the 
gastric  juice.  Tilanus  always  found  albumen,  together  with 
the  mucin,  in  the  synovia  within  the  joints.  This  fluid,  if  viewed 
anatomically,  must  be  regarded  as  serous,  because  secreted  by 
what  anatomists  term  serous  membrane.     In  a  chemical  point 


228  THE  CHEMISTRY  OF  THE  MOUTH. 

of  view,  it  must  be  considered  a  mucous  secretion  because  mucin, 
the  characteristic  ingredient  of  mucus,  is  contained  in  it. 

Simon  publishes  an  analysis  of  morbid  nasal  mucus  which 
used  to  accumulate,  in  thick  yellow  lumps,  in  the  upper  part  of 
the  nose  of  a  man  aged  thirty  years.  It  contained  an  unusual 
number  of  epithelium  cells,  and  a  few  mucous  corpuscles,  con- 
nected by  a  pretty  thick  membrane  of  coagulated  mucin.  It 
contained : — 

Water 880.0 

Solid  constituents         .         .         .         120.0 

Fat,  containing  cholesterin  .         .  6.0 

Caseous  matter,  with  pyin  or  mucin 

in  solution         ....  13.2 

Extractive  matters,  with  lactates 

and  chloride  of  sodium      .         .  12.0 

Albumen,    cells,    and   coagulated 

mucin      .....  84.0 


1000.0 


From  the  resemblance  of  mucin  to  the  protein  compounds,  we 
may  infer  that,  on  decomposition,  it  would  undergo  the  same 
metamorphosis  and  generate  the  same  acids,  and  consequently 
exert  the  same  influence  over  the  teeth  as  these  bodies  do  while 
undergoing  putrefaction.  How  an  excess  of  normal  mucus 
might  aifect  these  organs,  it  is  of  course  impossible  to  determine, 
so  long  as  we  are  ignorant  of  the  nature  of  the  free  acid  which 
it  contains. 

The  analysis  of  mucus  is  rendered  difficult  by  the  impossibility, 
in  many  cases,  of  separating  the  solution  of  mucin  from  the 
cells  which  accompany  it.  When  it  is  not  soluble  in  water,  it 
can  only  be  estimated  by  filtering  it  after  treating  it  with  dilute 
ammonia.  Unfortunately,  however,  the  swollen  epithelial  cells 
obstruct  the  filtration.  Should  the  filtration  be  successful,  the 
mucin  is  thrown  down  from  the  neutral  or  feebly  acid  solution 
with  alcohol,  and  from  the  alkaline  solution  by  dilute  acetic 
acid.  The  precipitate  must  be  washed  with  hot  spirit,  dried  at 
248°,  and  washed  again  with  hot  water.  The  rinsings  must  be 
collected,  and  immediately  evaporated  with  the  spirituous  solu- 


MUCUS.  229 

tion  filtered  off  from  the  mucin,  and  the  residue  must  be  extracted 
with  ether,  alcohol,  and  water. 

The  presence  of  albumen  increases  the  difficulties.  "If  the 
mucin,"  says  Lehmann,  "were  insoluble  in  water,  which  appears 
never  to  be  altogether  the  case,  the  separation  of  the  soluble 
albumen  from  the  insoluble  mucin  might  be  very  easily  effected; 
but  this  is  by  no  means  the  case  ;  for  the  swollen,  gelatinous,  or 
apparently  coagulated  mucin  only  gives  up  the  albumen  to  the 
water  with  difficulty  and  after  a  long  time.  Hence,  it  is  neces- 
sary, if  we  desire  to  obtain  a  comparatively  successful  result,  to 
distribute  the  mucus  repeatedly  in  water,  and  after  suffering  it 
to  form  a  deposit,  to  pour  only  the  clear  fluid  upon  the  filter,  re- 
peating the  process  till  the  filtered  fluid  no  longer  exhibits  any 
opalescence  on  heating;  for  the  insoluble  mucous  residue  cannot 
be  collected  on  the  filter  until  the  albumen  has  been  completely 
removed.  The  quantity  of  the  latter  may  be  determined  by  the 
ordinary  rules,  and  a  farther  separation  of  the  mucin  from  the 
epithelium  may  then  be  effected  by  means  of  diluted  alkalies." 

1^  jyyin  also  be  present,  the  albumen  must  first  be  separated 
by  boiling,  and  its  quantity  determined,  after  which  the  pyin 
may  be  thrown  down  by  acetic  acid. 

Of  the  quantity  of  mucus  secreted  by  the  membranes  in  a 
state  of  health,  it  is  impossible  to  form  any  idea.  Valentin  be- 
lieved it  to  be  exceedingly  small,  or  even  nothing  at  all  in  the 
normal  condition.  It  can  never  be  obtained  from  living,  healthy 
animals,  in  sufficient  quantities  for  analysis,  but  must  be  scraped 
from  the  mucous  membrane  of  animals  immediately  after  death. 

Lehmann  believes  that  the  formation  of  mucus  is  not  limited 
to  a  definite  spot  or  associated  with  any  definite  tissue.  "  The 
conversion  of  Wharton's  gelatine  into  a  substance  perfectly  simi- 
lar to  mucus  in  respect  to  its  physical  and  chemical  properties, 
the  gradual  transition  of  the  colloid  mass  of  many  cysts  into  per- 
fect mucus,  and  its  occurrence  in  many  exudations  proceeding 
from  serous  membranes,  are  facts  which  cannot  be  lost  sight  of 
in  our  consideration  of  the  origin  of  mucus.  Tilanus  has  drawn 
special  attention  to  the  circumstance  that  epithelial  structures 
are  always  present  wherever  there  is  true  mucus.  This  observa- 
tion might  lead  to  the  assumption  that  the  formation  of  mucus 


230  THE  CHEMISTRY  OF  THE  MOUTH. 

is  connected  with  the  development  of  certain  cells ;  that  is  to 
say,  that  its  production  occurs  simultaneously  with  the  develop- 
ment of  certain  morphological  elements.  Two  views  here  pre- 
sent themselves  for  our  consideration  ;  one  of  which  is  that  the 
albuminates  of  the  liquor  sanguinis  become  decomposed,  under 
certain  hitherto  unknown  conditions,  into  the  substratum  of  the 
epithelial  cells  and  into  mucus,  whereas  the  latter  substance  might, 
in  some  respects,  be  considered  as  a  secondary  product  of  this  cell- 
formation,  so  that  the  mucous  juice  in  the  mucus  would  hold  the 
same  relation  to  the  epithelial  cells  as  the  spirituous  fluid  does  to 
the  yeast  cells  in  a  mixture  which  has  undergone  fermentation. 
The  other  view,  which  seems  to  be  supported  by  numerous  ob- 
servations made  by  Scherer  and  Virchow,  refers  the  origin  of 
the  mucus  to  a  partial  disintegration  of  the  epithelial  cells.  All 
who  have  followed  Frerichs  in  his  observations  on  the  meta- 
morphosis of  the  cells  within  the  gastric  juice,  or  who  have 
examined  them  by  the  microscope  in  the  preparation  of  artificial 
gastric  juice,  will  easily  comprehend  the  gradual  solution  of  the 
gastric  cells,  and  their  conversion  into  a  mucous  fluid.  Such  a 
conversion  of  cells  into  a  mucous  substance  would,  therefore,  at 
all  events,  not  be  without  analogy.  Scherer  and  Virchow,  how- 
ever, go  still  farther,  and  advance  the  opinion,  based  upon 
several  pathologico-histological  observations  and  chemical  ex- 
periments, that  certain  colloid  substances,  and  others  adapted 
for  the  formation  of  urine,  may  be  converted  into  mucus  under 
conditions  which  still  remain  to  be  explained,  and  even  without 
any  cell  formation  ;  and,  hence,  they  regard  the  latter  mode  of 
development  as  associated  with  the  existence  of  colloid  or  carti- 
laginous substances.  This  view  is  supported  not  only  by  the 
absence  of  epithelial  structures  in  many  mucus-containing  cysts, 
but  more  especially  by  the  frequently  noticed  conversion  of  the 
gelatine  of  Wharton  into  perfect  mucus.  It  appears  to  us  still 
to  require  accurate  chemical  experiments,  to  decide  which  of 
these  two  hypotheses  merits  the  preference.  The  elementary 
analyses  which  were  made  by  Scherer  on  a  single  variety  of 
mucous  juice,  unfortunately  do  not  enable  us  to  decide  the  ques- 
tion, both  because  the  atomic  weight  could  not  be  determined, 
and  because  we  are  still  entirely  deficient  in  an  accurate  analysis 


SALIVARY  CALCULI.  231 

of  the  epithelial  cells,  the  colloid  substance,  &c.  It  remains  for 
us  to  hope  that  the  investigating  powers  of  men  like  Scherer 
may,  before  long,  enrich  science  with  the  knowledge  necessary 
for  elucidating  a  subject  which  is  so  intimately  associated  with 
the  advancement  of  physiology."* 

The  uses  of  mucus  are  to  act  as  a  protecting  medium  to  the 
parts  which  it  covers. 


CHAPTER    V. 

SALIVARY  CALCULI. 

We  have  deferred  the  consideration  of  these  concretions  till 
after  treating  of  mucus ;  for,  though  they  are  chiefly  formed 
from  saliva,  yet  the  mucus  of  the  mouth  furnishes  no  inconsider- 
able portion  of  their  bulk.  A  distinction  must,  however,  be 
made  in  these  concretions.  It  has  been  customary  among  den- 
tists to  consider  all  the  crusts  forming  upon  the  teeth  as  salivary 
calculus.  In  accordance  with  this  universal  custom,  we  shall 
treat  of  these  concretions,  commonly  called  tartar,  under  this 
head.  The  true  salivary  calculus,  however,  according  to  medi- 
cal parlance,  is  another  thing  altogether.  It  includes  only  the 
concretions  which  occasionally  block  up  the  salivary  ducts. 

These  true  salivary  concretions  fortunately  are  not  common 
in  man,  but  are  of  frequent  occurrence  in  the  ass  and  horse. 
They  consist  chiefly  of  earthy  carbonates  mixed  with  phosphates 
and  animal  matters.  We  copy  three  analyses  from  Simon, 
which  will  give  an  idea  of  the  constitution  of  the  calculi  found 
in  these  animals. 


From  an  ass. 

From  a  horse. 

From  a  horse. 

CAVENTOn. 

Lassaigne. 

Henry. 

Carbonate  of  lime 

91.6 

84 

85.62 

Carbonate  of  magnesia 

7.56 

Phosphate  of  lime 

4.8 

3 

4.40 

Animal  matter  soluble  in  water 

3.6 

9 

2.42 

Water 

3 

*  Lehmanr 

1,  op.  cit. 

232 


THE  CHEMISTRY  OF  THE  MOUTH. 


Poggiale  analyzed  a  calculus  taken  from  a  man.  It  was  hard, 
round,  tuberculated,  of  a  yellow  color,  and  easily  pulverized. 
It  contained  94?-  of  phosphate  of  lime,  with  mucus  and  animal 
matter. 

"Wurzer  analyzed  a  calculus  from  the  submaxillary  gland  of  a 
man.  It  weighed  three  grains,  was  oval,  of  a  grayish-white 
color,  and  consisted  principally  of  carbonate  of  lime  and  earthy 
phosphates,  with  traces  of  iron  and  manganese. 

Yon  Bibra,  of  Erlangen,  was  fortunate  enough  to  meet  with 
eleven  of  these  concretions  in  one  man,  a  peasant,  twenty-two 
years  of  age.  Their  specific  gravity  varied  from  1.437  to  0.933. 
He  examined  one  of  the  lighter  calculi,  and  has  published  his 
analysis.  He  found  it  to  consist  of  a  nucleus  made  up  of  albu- 
men and  mucus,  round  which  the  rest  of  the  calculus  had  been 
gradually  deposited  in  concentric  layers,  as  is  the  case  with 
urinary  and  other  calculi.  These  layers  were  made  up  of 
various  salts  intermixed  with  animal  matter,  as  will  be  seen  by 
the  subjoined  table  : — 

Phosphate  of  lime  .....       38.2 


Carbonate  of  lime 

.       13.3 

Phosphate  of  magnesia 

Fatty  matter  with  traces  of  soda    . 

5.1 
3.1 

Organic  matter      .... 
Water 

.       35.0 

5.3 

100.0 

In  comparing  these  results  with  those  obtained  by  Caventou, 
Lassaigne,  and  Henry,  the  reader  will  be  struck  with  the  great 
excess  of  phosphates  in  human  calculi,  as  compared  with  the 
concretions  taken  from  the  lower  animals. 

Of  tartar,  there  have  been  few  analyses,  and  these  have  not  been 
very  satisfactory.  Writers  on  dentistry  make  several  varieties 
of  this  deposit,  but  chemists  have  not  as  yet,  as  far  as  the 
author  is  aware,  analyzed  these  different  varieties.  It  was  the 
intention  of  the  writer  to  have  made  a  series  of  analyses  for  this 
volume ;  but,  though  he  applied  early  to  his  dental  friends,  he 
failed  to  secure  specimens  for  the  purpose. 


SALIVARY  CALCULI. 

According  to  Berzelius,  tartar  contains  ; — 

Phosphates  of  lime  and  magnesia     . 
Salivary  (?)  mucus  ..... 

Ptyalin  ....... 

Animal  matter  soluble  in  hydrochloric  acid 


233 


79.0 

12.5 

1.0 

7.5 

100.0 


Vauquelin   and  Laugier  have  published  the  following   ana- 
lysis : — 


Phosphate  of  lime,  with  a  little  magnesia    . 
Carbonate  of  lime      .         .         .         .         . 
Salivary  mucus  (including  ptyalin  ?)    . 
Animal  matter  soluble  in  hydrochloric  acid 
Water  and  loss  .         .         .         .         . 


6G 
9 

18 
5 

7 

100 


Still  farther  to  elucidate  this  subject,  the  analyses  of  Pepys 
and  Dr.  Dwindle,  of  Cazenovia,  New  York,  copied  from  Dr. 
Harris's  work  on  dental  surgery,  are  subjoined: — 


Pepys. 

Dwjnelle 

Phosphate  of  lime 

.     35 

60 

Carbonate  of  lime 

14 

Fibrin,  or  cartilage  (?) 

.       9 

Animal  matter  and  mucus  . 

16 

Animal  fat,  or  oil       . 

.       3 

Water  and  loss 

.       3 

10 

50 


100 


For  the  sake  of  comparison,  and  to  elucidate  the  probable 
source  of  this  deposit,  an  analysis  by  Wurzer  of  a  concretion 
formed  in  one  of  the  tonsils  is  appended.  It  was  of  a  grayish- 
white  color,  marked  with  rose-red  spots,  and  verrucose ;  inter- 
nally it  presented  no  appearance  of  lamellae,  although  it  contained 
an  oval  nucleus. 


234  THE  CHEMISTRY  OF  THE  MOUTH. 

Phosphate  of  lime 63.8 

Carbonate  of  lime  ......  16.7 

Animal  matter        ......  13.3 

Ptyalin  with  chlorides  of  sodium  and  potassium  7.1 

Iron  and  traces  of  manganese           ...  .1 

The  presence  of  ptyalin  in  the  above  compound  leaves  no  doubt 
that  saliva  assisted  at  least  in  its  formation,  and  the  close  resem- 
blance between  it  and  tartar  would  seem  to  imply  an  identity  of 
origin.  Jourdain's  notion  of  a  specific  glandular  apparatus  for 
the  secretion  of  this  substance  must  be  given  up,  since  his  tartar 
glands  have  been  proved  to  be  salivary  glands,  and  since  there 
is  so  strong  a  resemblance  between  tartar  and  true  salivary 
concretions.  The  mucus  of  the  mouth  undoubtedly  enters  into 
the  composition  of  this  concretion,  so  that  we  find  it  to  be  only 
a  deposit  from  the  fluids  of  the  mouth  upon  the  teeth,  varying 
of  course  as  the  fluids  vary,  and  being  soft  or  hard,  as  it  con- 
tains more  or  less  animal  matter. 


BOOK  lY. 

CHEMISTRY  AND  METALLURGY  OF  THE  METALS  AND 
EARTHS  USED  BY  THE  DENTIST. 


PART    I. 

THE     METALS. 

CHAPTER   I. 

THE  VARIOUS  METHODS  OF  APPLYING  HEAT,  FURXACES,  AND 
AUXILIARY  APPARATUS. 

The  chemist  and  the  metallurgist  find  it  very  necessary  to  be 
acquainted  with  that  branch  of  science  known  as  ^ronomics^^ 
especially  with  its  practical  results.  Few  agents  are  more  power- 
ful than  heat  in  producing  chemical  changes,  whether  of  composi- 
tion or  of  decomposition.  It  possesses  the  power  of  superseding 
common  affinities  ;  or,  to  speak  more  philosophically,  at  different 
degrees  of  heat,  the  chemical  affinities  of  bodies  are  found  to 
differ  greatly. 

Thus,  when  nitric  acid  and  copper  are  brought  together  at 
the  ordinary  temperature  of  the  atmosphere,  a  blue,  deliquescent 
nitrate  of  copper  is  formed ;  but  if  the  acid  be  cast  upon  red- 
hot  copper,  or  if  the  salt  just  mentioned  be  heated  to  redness, 
the  amorphous  black  oxide  of  the  metal  is  formed.  So,  too,  if 
charcoal  be  mixed  with  a  metallic  oxide  at  common  tempera- 
tures, no  change  takes  place  ;  but,  if  a  strong  heat  be  applied, 
the  carbon  combines  with  the  oxygen  of  the  oxide,  carbonic  acid 
is  evolved,  and  the  pure  metal  remains  behind.     In  the  latter 


236   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

example,  we  find  a  total  difference  in  the  affinities  of  charcoal 
and  oxygen  at  different  temperatures.  The  metallurgist  con- 
stantly takes  advantage  of  this  peculiar  power  of  increments  of 
heat  in  modifying  the  composition  of  bodies.  By  means  of  this 
property,  he  deprives  the  metals  at  one  time  of  sulphur  or 
arsenic,  at  another  of  oxygen ;  varying  his  manipulations  with 
the  necessities  of  the  case. 

Heat  is  also  used  to  modify  the  physical  state  of  bodies. 
Water  is  a  familiar  example  of  this  property  of  heat.  This  sub- 
stance occurs  in  three  different  conditions,  which  are  determined 
by  the  degree  of  heat  to  which  it  is  subjected.  At  32°  F.  and 
below  it,  water  is  solid  ice  ;  between  32°  and  212°,  it  is  a  liquid  ; 
at  212°  it  is  a  gas  or  vapor.  Any  other  body  may  also  be  made 
to  assume  these  three  conditions,  if  the  necessary  increments  or 
decrements  can  be  obtained.  Thus,  we  can  volatilize  metals, 
converting  them  into  vapor  by  a  high  heat ;  or,  on  the  other 
hand,  we  can  freeze  gases  to  solids  by  exposing  them  to  intense 
cold.  We  may,  therefore,  infer  that  all  bodies  are  capable  of 
assuming  these  three  forms ;  and  that,  in  those  cases  in  which 
we  cannot  exhibit  them  thus  modified,  the  cause  of  our  failure 
is  to  be  found,  not  in  the  bodies  themselves,  but  in  our  limited 
control  over  the  powers  of  nature.  Were  our  means  of  raising 
or  depressing  temperature  sufficiently  great,  we  might  hope  to 
exhibit  hydrogen  as  a  solid,  or  iridium  as  a  gas. 

The  point  that  the  practical  metallurgist  desires  to  obtain  is 
far  below  these  extremes  of  the  powers  of  cold  and  heat.  He 
wishes,  sometimes,  to  fuse  the  metals  on  which  he  is  working, 
since  he  can  control  them  more  readily  in  a  liquid  state,  some- 
times only  to  soften  without  melting  them,  as  when  iron  needs 
to  be  welded.  For  this  purpose,  he  needs  some  knowledge  of 
the  higher  degrees  of  heat,  as  metals  are  of  very  diffe^nt  fusi- 
bility. Mercury,  for  example,  is  fluid  at  a  far  lower  tempera- 
ture than  that  at  which  water  is  converted  into  ice,  and  iridium 
has  resisted  all  the  most  intense  heats  which  the  chemist  knows 
how  to  apply. 

So  various  are  the  fusing  points  of  the  metals,  that  very  dif- 
ferent kinds  of  apparatus  are  employed  for  their  treatment. 
Those  which  come  under  our  observation  are  not  very  numerous, 
and  will  therefore  be  treated  of  somewhat  in  detail. 


METHODS  OF  APPLYING  HEAT,  FUKNACES,  ETC.  237 


THE    BLOWPIPE. 

For  the  minor  operations  in  which  heat  is  employed,  the  blow- 
pipe is  the  most  common  as  well  as  the  most  useful  instrument. 
The  simplest  form  of  this  implement  is  that  which  is  used  by 
jewellers,  gas-fitters,  and  others.  It  is  a  simple  tube  of  brass, 
or  other  metal,  tapering  gradually  to  one  end,  at  which  it  is 
curved.  This  extremity  contains  a  very  fine  orifice,  which  is 
sometimes  protected  by  a  raised  margin. 


Fig.  24. 


^ 


The  fine  point  of  the  blowpipe  is  held  against  the  side  of  the 
flame  of  a  lamp,  and  a  steady  blast  of  air  from  the  mouth  urged 
through  it.  The  heat  is  very  highly  increased  by  this  method, 
for  reasons  which  we  shall  presently  specify  when  we  come  to 
give  an  account  of  the  flame.  When  the  time  during  which  the 
blowpipe  is  to  be  used  is  short,  this  form  of  it  answers  every 
purpose.  When,  however,  the  instrument  is  required  to  be 
longer  used,  the  moisture  from  the  lungs  accumulates  in  the 
tube,  produces  irregularities  in  the  blast,  and  spirts  upon  the 
substance  operated  on,  to  the  great  annoyance  of  the  workman. 

Fig.  25. 


The  common  method  of  obviating  this  will  be  understood  by 
a  reference  to  the  above  figure.  It  consists  in  appending  a 
globular  chamber  to  the  pipe,  so  that  the  moisture  may  collect 
in  it  and  escape  the  direct  influence  of  the  blast.  It  was  Cron- 
stedt  who  first  introduced  this  improvement,  and  it  certainly 
does  obviate  the  diflficulty  to  a  very  considerable  extent.  But 
it  does  not  wholly  get  rid  of  the  annoyance  ;  for,  if  the  blowpipe 
is  at  all  inclined,  during  a  protracted  operation,  the  water  runs 
from  the  bulb  and  chokes  the  pipe  again. 


238     CHEMISTRY  OP  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Wollaston  contrived  a  blowpipe,  -which  is  very  ingenious  and 
portable,  but  which  is  liable  to  the  same  objections  as  the  com- 


Fig.  26. 


Fig.  27. 


^    4 


m 


H 


mon  instrument,  in  containing  no  chamber  to  collect  the  moisture 
of  the  breath.  It  is  composed  of  three  pieces,  a,  h,  c.  The 
small  end  of  a  fits  into  the  large  end  of  b,  which  is  closed  at  its 
small  end,  and  perforated  in  one  side  by  a  narrow  orifice.  The 
piece  c  is  closed  at  its  wider  end,  and  slipped  over  the  top  of  b 
by  means  of  the  opening  e,  which  is  so  graduated  that,  when  it  is 
forced  down  as  far  as  it  will  go,  the  hole  d  in  the  side  of  b  will 
exactly  correspond  with  the  narrow  canal  of  c. 

Gahn's  instrument  is  that  which  is  commonly  preferred  by 
blowpipe  manipulators.  It  is  composed  of  three  parts,  the  chief 
of  which  is  a  chamber,  of  a  cylindrical  form,  an  inch  in  length  and 
half  an  inch  in  transverse  diameter.    Into  the  upper  end  of  this 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  239 

cylinder  is  screwed  a  long  tube,  which  tapers  from  the  mouth-piece 
to  the  chamber.  A  shorter  piece,  narrowing  to  a  fine  point,  is 
fitted  to  the  side  of  the  chamber.  This  piece  is  tipped  at  its  free 
end  with  a  conical  piece  of  platinum,  which  is  separate  from  the 

Fig.  28. 


pipe,  and  can  be  applied  or  removed  at  pleasure.     It  is     j,.    ng 
perforated  with  an  extremely  small  canal.     The  reason        a 
for  preferring  platinum  is  to  be  found  in  its  infusibility       ^ 
at  any  heat  to  which  the  workman  can  subject  it.    This 
affords  great  facility  for  the  removal  of  carbonaceous  matters 
which  often  clog  the  bore.     Nothing  more  is  necessary  than  to 
subject  it  to  a  very  high  heat  in  the  blowpipe  flame,  and  these 
impurities  are  burned  off.     When  moisture  collects  in  the  instru- 
ment, it  is  removed  by  disconnecting  the  parts,  blowing  through 
the  chamber,  and  wiping  it  with  a  dry  cloth. 

Mitscherlich  has  improved  this  blowpipe  by  rendering  it  port- 
able. The  chamber  (Fig.  30)  is  smaller,  and  attached  perma- 
nently to  the  longer  tube,  which  is  made  to  unscrew  in  the  mid- 
dle, so  that  the  short  tube  and  its  platinum  jet  can  be  introduced 
into  B,  and  the  upper  half,  A,  be  screwed  on. 

The  cheapest  form  of  the  improved  blowpipe  is  that  invented 
by  Dr.  Black  (Fig.  31).  It  is  made  of  tinned  iron,  japanned, 
and  consists  of  a  truncated  cone,  closed  at  its  lower  extremity, 
near  which,  at  the  side,  is  a  brass  tube,  supplied  with  many 
platinum  jets. 

The  best  material  for  constructing  a  blowpipe  is  silver.  The  jets, 
however,  ought  not  to  be  made  of  this  metal,  because,  although 
they  answer  very  well  for  a  time,  yet,  after  being  frequently 
subjected  to  high  heats,  they  are  apt  to  become  brittle.  After 
silver,  tinned  iron  is  to  be  preferred.  The  great  majority  of  the 
blowpipes  in  common  use  are  made  of  brass  ;  but  this  alloy  is 


240     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


Fig.  30. 


Fig.  31. 


O 


=*> 


objectionable,  on   account  of  its  easy  oxidation  and   the   ex- 
tremely unpleasant  odor  and  taste  which  it  acquires. 


LAMPS. 

Any  kind  of  flame  may  be  used  for  blowpipe  operations,  pro- 
vided it  be  large  enough.  Engestrom  and  Bergmann  used  com- 
mon candles,  but  they  are  objectionable  on  account  of  the  melt- 
ing of  the  tallow  on  the  side  towards  which  the  blast  is  urged, 
and  the  frequent  necessity  for  trimming  the  wick.  Spirit-lamps 
are  also  used,  but  they  do  not  give  so  much  heat  as  oil-lamps, 
and  their  only  advantage  is  their  cleanliness,  which  is  important 
when  glass  tubes  are  employed,  as  in  certain  examinations  of 
volatile  substances. 

The  common  form  of  the  dentist's  lamp  will  be  seen  in 
Fig.  32.  It  should  hold  at  least  a  pint,  and  have  a  spout 
three  or  four  inches  long  and  about  three-fourths  of  an  inch  in 
diameter.  When  spirit  is  used  (and  it  is  preferred  by  many  den- 
tists, among  them  Dr.  Harris),  the  wick  should  be  large  enough 
to  fill  the  spout  pretty  tightly.  Should  this  precaution  be  neg- 
lected, the  flame,  mixed  with  air,  may  extend  back  into  the 
lamp,  and  an  explosion  take  place. 

The  best  form  of  lamp  for  blowpipe  manipulations  is  that 
invented  by  Berzelius,  a  sketch  of  which  is  given  in  Fig.  33. 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


241 


The  movable  triangle  over  the  lamp  is  a  supplementary  appa- 
ratus for  the  purpose  of  receiving  small  crucibles  which  are  to  be 
subjected  to  the  action  of  the  flame.  The  lamp  itself  is  made 
of  tinned  iron  or  brass.     It  is  4|^  inches  long  and  tapering  some- 


Fig.  32. 


Fia;.  33. 


what  towards  the  bottom,  which  is  usually  narrower  than  the  top. 
At  one  end  of  the  upper  surface  is  an  opening  through  which 
the  lamp  is  filled.  This  ^is  closed  by  a  screw-cap  and  a  wash- 
leather.  At  the  other  end  is  a  wick-holder,  which  also  may 
be  covered  with  a  screw-cap.  The  object  of  these  covers  iA 
to  secure  the  oil  from  spilling,  and  so  to  render  the  lamp  porta-  ■ 
ble.  The  front  of  the  lamp  is  oblique,  to  permit  the  ready  de- 
flection of  the  flame.  Some  of  these  lamps  have  a  long  narrow 
wick-holder,  which  is  made  oblique  on  its  upper  surface.  The 
object  to  be  fused  is  held  at  the  side  on  which  the  wick  is  low, 
and  the  blowpipe  introduced  into  the  higher  end  of  the  flame. 
This  arrangement  secures  a  great  body  of  flame  and  a  corre- 
sponding intensity  of  heat. 

The  best  fuel  for  this  lamp  is  pure  olive  oil,  or  oil  of  rape. 
The  carbon  contained  in  their  flame  adds  considerably  to  their 
heating  power.     Sometimes  a  jet  of  common  coal  gas  is  used  for 
•  the  same  purpose,  but  this  is  inferior  to  oil  in  heating  power. 

J       Structure  of  Flame. — A  knowledge  of  the  nature  and  pro- 
perties of  flame  being  essential  to  every  blowpipe  manipulator, 
we  shall  give  a  brief  account  of  it. 
16 


242      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

The  flame  of  a  common  candle  is  a  type  of  all  other  flames, 
and  has,  therefore,  been  always  used  as  an  illustra- 
Fig.  34.        ^-Qjj  Qf  flame  in  general.     Flame  is  nothing  but  gas 
or  vapor  so  highly  heated  that  it  has  become  lumi- 
nous, its  brilliancy  depending  wholly  upon  its  che- 
mical composition.      Thus   the  flame   of  coal-gas, 
which  contains  much  carbon,  is  very  white  and  lumi- 
nous, whilst  that  of  pure  hydrogen  is  so  pale  as  to 
be  scarcely  visible  in  daylight,  or  even  in  the  pre- 
sence of  a  lighted  candle.     If  we  examine  closely 
the  flame  of  a  common  candle,  we  find  that  we  can 
easily  separate  it  into  several  parts.    iThat  portion 
of  the  flame  which  immediately  surrounds  the  wick, 
represented  in  the  figure  by  a,  b,  is  a  deep  beautiful 
blue.     This  portion  becomes  thinner  as  it  ascends  till  it  gradu- 
ally disappears.     It  owes  its  color  to  the  combustion  of  carbonic 
oxide,  and  is  the  coolest  portion  of  the  flame.  I 
I  The  centre  of  the  flame  is  dark  ;  that  is,  it  is  not  luminous. 
It  consists  of  the  gases  produced  by  the  decomposition  of  the 
fat,  and  is,  in  the  flame  we  are  considering,  highly  charged  with 
carbon.     These  gases  do  not  meet,  at  this  point,  with  sufiicient 
oxygen  to  burn  them,  and  therefore  remain  unchanged.*     This 
portion  is  represented  by  e. 

I  Surrounding  this  dark  spindle-shaped  centre,  we  observe  a 
'  brilliant  white  flame  d.  Here  the  gases  combine  with  the 
oxygen  of  the  atmosphere.  The  hydrogen,  it  is  commonly  said, 
burns  first,  and  the  intense  heat  generated  by  its  combustion, 
ignites  the  minute  particles  of  carbon  which  are  supposed  to  be 
held  in  suspension  by  the  ascending  gas. 

All  the  gas,  however,  is  not  burned  in  this  central  spire  of 
flame.  A  portion  of  it  escapes  and  burns  more  slowly,  in  con- 
sequence of  its  being  mixed  with  steam,  carbonic  acid,  and  other 
products  of  combustion,  together  with  a  little  unburnt  carbon. 
This  forms  the  outer  dimly  luminous  envelop  e,  which  surrounds 

*  To  prove  this,  introduce  a  tube  into  the  central  flame,  and  it  will  be 
found  that  the  gas  passing  through  it  can  be  burned  at  the  other  end, 
giving  a  flame  in  all  respects  like  that  formed  around  the  dark  centre. 


1 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  243 

all  flames.     The  maximum  heat  is  found  at  the  level  //,  from 
which  it  decreases  both  upwards  and  downwards.^ 

The   blowpipe  flame,  difi"ering  somewhat  from  the    common 
flame,  will  now  be  described.     It  consists  of 
two  distinct  parts,  one  formed  immediately  ^^"  '^■^' 

before  the  nozzle  of  the  blowpipe,  small,  blue, 
pointed  and  well-defined,  the  other  yellowish 
brown  and  vague. 

The  former  is  the  reducing,  the  latter  the 
oxidating  flame.     These  have  received  their  J\ 

names  from  the  fact  that  a  metallic  oxide, 
introduced  into  the  first  flame,  is  reduced  to  a  metal,  while,  in 
the  second,  metals  are  converted  into  oxides.  The  highest  heat 
is  just  beyond  the  apex  of  the  blue  flame,  and  it  is  at  the  same 
point  that  reduction  is  efi'ected,  by  means  of  the  unburned  carbon 
therein  contained. 

Oxidation  is  very  easily  effected.  All  that  is  necessary  is  to 
place  the  substance  at  or  a  little  beyond  the  extremity  of  the 
outer  flame,  and  to  accommodate  the  temperature  to  the  metal 
operated  on.  A  dull  red  is  the  best  heat  for  most  oxidations. 
Reduction  is  more  difficult,  and  requires  practice  and  skill  to 
accomplish  it  satisfactorily.  To  exercise  one's  self  in  it,  one  of 
the  best  plans  is  to  put  a  small  grain  of  tin  on  charcoal,  and 
urge  the  flame  upon  it.  A  coat  of  oxide  will  show  the  operator 
when  he  has  failed  to  produce  a  good  reducing  flame.  This  is 
attained  by  introducing  the  jet  into  the  body  of  the  flame,  so 
as  to  produce  a  small  dart,  and  by  using  a  smaller  orifice  than 
is  employed  for  oxidation. 

It  is  not  necessary  here  to  speak  of  supports  and  auxiliary 
apparatus.     The  dentist  uses  charcoal  as  a  support. 

TIlc  Blast. — To  produce  a  good  continuous  blast  from  the 
blowpipe,  necessary  as  it  is  to  the  manipulator,  is  difficult  to  the 
tyro,  and  requires  much  practice.  Verbal  instructions  cannot 
go  far  towards  enabling  a  student  to  accomplish  this  desirable 
result — it  is  only  to  be  attained  by  practice ;  but  a  few  hints 
may  aff'ord  some  clue  to  the  beginner  who  is  attempting  to 
acquire  this  art. 

"The  practice,"  says  Faraday,  "necessary,  in  the  first  place, 
is  that  of  making  the  mouth  replace  the  lungs  for  a  short  time. 


24-i      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

by  using  no  other  air  for  the  blowpipe  than  that  contained  in 
it."  MitchelVs  directions  in  regard  to  this  matter  are  so  simple 
and  clear  that  we  transcribe  them : — 

"Let  the  student  first  observe,  that  it  is  easy,  after  having 
closed  the  lips,  to  fill  the  mouth  with  air  and  to  retain  it  so,  at 
the  same  time  that  respiration  may  be  carried  on ;  and  if,  while 
the  mouth  is  in  this  state,  a  blowpipe  be  introduced  between 
the  lips,  it  will  be  found  that  the  small  quantity  of  air  which  its 
jet  allows  to  pass  through  it,  will  be  amply  supplied,  for  ten  or 
fifteen  seconds,  by  the  quantity  contained  in  the  mouth  ;  and 
this  being  repeated  a  few  times,  a  ready  facility  for  using  the 
blowpipe,  independently  of  the  lungs,  will  be  acquired. 

"  This  step  being  taken,  the  next  is  to  combine  this  process  with 
the  ordinary  one  of  propelling  air  directly  from  the  lungs  through 
the  mouth,  in  such  a  way  that  when  the  action  of  the  lungs  is 
suspended  during  inspiration,  the  blast  may  be  continued  by  the 
action  of  the  mouth  itself,  from  the  air  contained  within  it. 
The  time  of  fourteen  or  fifteen  seconds,  during  which  the  mouth 
can  supply  air  independently  of  the  lungs,  is  far  more  than  can 
be  required  for  one  or  even  many  more  inspirations,  and  all  that 
is  required  to  acquire  the  necessary  habit  is  the  power  of  open- 
m(r  and  closinj:  the  communication  between  the  mouth  and  the 
lungs  and  between  the  air  and  the  lungs  at  pleasure. 

"  The  capability  of  closing  the  passages  to  the  nostrils  is  very 
readily  proved ;  every  one  possesses  and  uses  it  when  he  blows 
from  the  mouth,  and  that  of  closing  or  opening  the  mouth  to 
the  lungs  may  be  acquired  with  equal  readiness.  Applying  the 
same  blowpipe  to  the  lips  as  before,  use  the  air  in  the  mouth  to 
produce  a  current,  and,  when  it  is  about  half  expended,  open 
the  lungs  to  the  mouth,  so  as  to  replace  the  air  which  has  passed 
through  the  blowpipe ;  again,  cut  ofi"  the  supply,  as  at  first,  but 
continue  to  send  a  current  through  the  instrument,  and,  when 
the  second  mouthful  of  air  is  nearly  gone,  renew  it,  as  before, 
from  the  lungs. 

"  To  some  this  may  be  difficult ;  but  if  the  preceding  instruc- 
tions be  followed  and  persevered  in  for  a  short  time,  a  continuous 
blast  may  be  kept  up  from  ten  minutes  to  a  quarter  of  an  hour, 
without  any  other  inconvenience  than  the  mere  lassitude  of  the 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


245 


lips,  caused  by  compressing 
the  mouth-piece  of  the  instru- 
ment."* 

Self-Acting  Blowpipes.  — 
These  are  nothing  but  modifi- 
cations of  the  blast-lamp.  The 
simplest  form  of  this  instru- 
ment is  the  common  Russian 
lamp,  so  generally  used  that 
it   must   be  familiar  to  most 


Fig.  36. 


Fig.  37. 


a,  a.  Side  of  c:ise.  b.  Top  of  case  thrown  back.  c.  Front  of  case,  united  by  hinge  at  bottom,  and 
shown  in  a  horizontal  position,  d,  d.  An  oblong  fluid  vessel  for  reception  of  alcohol,  e.  Vent  to 
vessel  d  d.  for  introduction  of  fluid,  f.  Burner  introduced  in  groove  of  vessel  d  d.  g.  g.  Movable 
extinguisher  to  burner  /,  and  not  for  working  the  same.  h.  Horizontal  plate  of  tin  for  sustaining 
copper  globe  in  place,  i.  Copper  globe.  j,j.  An  oblong  vessel  for  the  reception  of  alcohol.  7.'. 
Vent  to  vessel  j  j.  for  feeding  the  same  with  fluid.  I.  Burner,  extending  from  fluid  in  j  j.  m.  Ex- 
tinguisher to  burner  I.  n.  Siphon,  extending  from  fluid  in  vessel  J,/,  to  near  the  bottom  of  globe  i'. 
o.  Stopcock  to  siphon,  p.  Blowpipe  from  top  of  globe  i.  q.  A  small  copper  trough  for  retaining 
condensed  vapor  that  escapes  from  blowpipe. 

The  manner  of  working  Dr.  Parmly's  self-acting  blowpipe  is  very  simple.  The  two  vessels,  d  d 
a.nd.jj,  being  filled  with  alcohol,  the  stopcock  o  is  closed.  The  mouth  is  then  applied  to  the  end  of 
the  blowpipe  p,  and  the  atmospheric  air  exhausted  from  the  globe.  AVhen  the  stopcock  is  turned, 
the  alcohol  in  vessel  J  will  rush  through  the  siphon  and  fill  the  globe,  should  the  air  continue  to 
be  exhausted.  For  all  practical  purposes,  the  globe  should  be  only  partially  filled,  and  the  stop- 
cock turned  so  as  to  close  the  siphon.  The  burner/ should  be  ignited,  and,  in  about  five  minutes, 
alcoholic  vapor  will  be  seen  to  rush  out  from  blowpipe  p,  when  the  burner  I  should  be  ignited. 
The  volume  of  flame  can  be  governed  by  the  extinguishers  g  and  m. 

^Vhen  the  lamp  is  used  for  melting  metal  for  castings,  the  metal  should  be  placed  in  an  iron 
ladle,  and  this  latter  in  the  furnac«  previously  filled  with  charcoal,  and  placed  in  a  proper  position, 
as  represented  in  Fig.  37,  for  the  flame  of  the  lamp  to  be  thrown  into  it  against  the  coaL  When  it 
is  desired  to  melt  gold,  a  crucible  should  be  used  instead  of  the  iron  ladle. 


*  Manual  of  Assaying,  p.  109. 


246     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Fig.  38. 


a,  a.  Air-pipe  leading  from  the  bellows  to  the  lamp.  6.  Tapor-pipe.  c,  c,  c.  A  round  bellows,  ten 
inches  in  diameter,  d.  A  rod  attached  to  the  upper  movable  head  of  the  bellows  and  passing 
through  cro3?piece  e,  which  serves  to  keep  the  head  in  a  horizontal  position.  /.  A  rod  attached  in 
a  similar  manner  to  the  lower  movable  head  of  the  bellows,  and  passing  down  through  the  table. 
g.  A  stirrup  attached  at  the  upper  end  to  shaft  h  h .  i,  i.  Support  for  shaft  hh;  \>j  means  of  an 
arm  projecting  backwards  from  shaft  h  h,  and  attached  to  the  lower  end  of  rod  /,  the  force  is  com- 
municated from  the  foot  of  the  artist  to  the  bellows. 

readers.  It  consists  of  a  strong  double  copper  cylinder,  from 
the  outer  cavity  of  which  a  jet  pipe  passes  into  the  central  cylin- 
der. The  outer  cylinder  being  filled  and  the  inner  half  filled 
with  alcohol,  the  spirit  in  the  latter  is  set  fire.     The  boiling 


METHODS  OP  APPLYING  HEAT,  FURNACES,  ETC. 


247 


alcohol  in  the  outer  cylinder  is  thrown  out  in  a  strong  jet, 
which  takes  fire  and  produces  a  very  intense  heat. 

Dr.  Jahiel  Parmly,  of  New  York,  has  invented  a  blowpipe  of 
this  kind,  of  which  we  give  a  cut  (Fig.  37).  A  small  furnace 
accompanies  it,  which  is  used  for  heating  pieces  preparatory  to 
soldering  and  for  fusing  metals. 

Dr.  Elliott,  of  Montreal,  has  added  to  this  an  improvement 
(Fig.  38)  by  which  he  gets  all  the  benefit  of  the  blast-lamp, 
together  with  the  advantages  of  an  atmospheric  blowpipe.  His 
improvement  consists  in  the  introduction  of  a  bellows,  the  jet  of 
which  terminates  within  the  vapor  flame.  This  gives,  of  course, 
a  true  blowpipe  flame,  having  the  maximum  heat,  as  usual,  at 
the  apex  of  the  blue  flame.  This  lamp  is  used  for  soldering, 
the  vapor  flame  keeping  the  whole  piece  redhot,  while  the  tip 
of  the  blue  dart  may  be  concentrated  upon  the  point  at  which 
the  greatest  heat  is  needed. 

Table  Blow])ipe. — This  is  designed  for  more  protracted  ope- 
rations and  hio-her  heats  than  those  which  have  been  already 


Fig.  39. 


Fig.  40. 


alluded  to.  It  consists  of  a  cylinder  piston  (2),  which  drives  the 
air  into  a  chamber  (1)  when  worked  by  the  treadle  (4).  The 
blast  passes  through  the  pipe  (3),  which  may  either  be  attached 
to  a  movable  jet,  or  pass  into  the  interior  of  an  Argand  burner, 
as  in  Fig.  40.  This  burner  is  supplied  with  gas  or  oil  from  a 
movable  reservoir.     There  are  several  modifications  of  it,  ac- 


248      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

commodating  it  both  to  blowpipe  operations  and  to  the  portable 
blast  furnace. 

FURNACES. 

The  modifications  of  furnaces  to  meet  the  various  necessities 
of  the  arts  are  almost  endless.  There  are,  however,  a  few  gene- 
ral principles  which  govern  the  builder,  and  to  them  it  is  proposed 
to  call  attention  in  the  present  section. 

The  first  great  division  is  into  hlast^  and  wind,  or  air  furnaces. 
The  latter  have  received  their  name  from  the  fact  that  all  the 
draught  in  them  is  obtained  by  the  construction  of  the  chimney, 
as  it  is  in  a  common  fireplace,  while  the  former  are  urged  by 
an  artificial  blast  thrown  in  at  the  tuyere. 

In  air  furnaces,  the  heat  is  applied  to  the  substance  to  be 
heated,  by  bringing  it  in  direct  contact  with  the  fuel,  as  in  the 
common  wind  furnace,  or  by  placing  it  where  the  flame  will  play 
over  it,  as  in  the  reverheratory  or  fiame  furnace.  {Flammofen 
of  the  Germans.) 

The  ordinary  construction  of  a  wind  furnace  is  represented  in 
Fig.  41.  A  is  the  body  of  the  furnace,  which  is  open  at  top 
for  the  admission  of  fuel,  &c.  During  working,  it  is  closed  by 
the  movable  slide  a,  which  is  made  of  fire-brick,  in  one  piece,  or 
oftener  of  a  strong  iron  frame,  filled  in  with  brick.  In  any  case, 
a  hole  is  left  in  the  middle  of  the  slide,  provided  with  a  fine 
clay  stopper,  which  may  be  removed  from  time  to  time,  to  per- 
mit the  manipulator  to  examine  the  progress  of  his  work.  The 
draft  passes  through  the  opening  B  into  the  chimney  C.  The 
bars  of  the  grate  which  separate  the  body  of  the  furnace 
from  the  ash-pit  h  are  movable,  that  they  may  be  easily  replaced 
when  burned  out.  Supports,  made  of  fire-brick,  rest  upon  the 
bars  of  the  grate,  and  upon  these  supports  the  crucibles  stand 
during  each  operation.  All  such  furnaces  should  be  supplied 
with  a  hood  D. 

The  power  of  such  a  furnace  as  this  depends  entirely  upon 
its  dimensions  and  the  height  of  its  chimney.  The  most  eco- 
nomical size  is  that  which  will  contain  four  ordinary  crucibles. 
This  allows  plenty  of  room  for  one  large  operation,  or  for  several 
small  ones  conducted  at  the  same  time.    Fourteen  inches  square 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


249 


by  twenty-four  deep,  from  the  bottom  of  the  cover  to  the  bai's, 
is  a  convenient  size,  though  for  many  purposes,  such  a  bulk  of 
fuel  as  a  furnace  of  this  size  would  consume  is  unnecessary. 
The  bars  should  be  made  of  1^  inch  iron,  and  should  be  from 

Fig.  41. 


J  an  inch  to  an  inch  apart,  as  the  combustibility  of  the  fuel  may 
require.  With  a  chimney  30  feet  high,  receiving  no  other  flues, 
such  a  furnace  as  this  is  capable  of  making  an  iron  assay.  A 
damper  is  sometimes  introduced  into  the  chimney,  in  order  to 
regulate  the  draft. 

For  other  purposes,  smaller  furnaces  should  be  used.  The 
following  figure  represents  the  section  of  one  described  by  Morfit, 
in  his  Chemical  and  Pharmaceutical  Manipulations.  The  first 
part  of  the  flue,  passing  ofi"  from  the  body  of  the  furnace,  is 
covered  in  with  a  sand-bath,  and  closed  below  with  an  iron  plate. 
The  flue  descends  before  passing  into  the  chimney,  thus  leaving 
between  it  and  the  ash-pit  a  hot-air  chamber,  in  which  all  the 
common  desiccations  may  be  performed.  Another  sand-bath 
closes  the  furnace  itself,  instead  of  the  slide  already  described. 


250      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

It  is  useless  to  point  out  the  advantages  and  the  economy  in 
fuel  resulting  from  such  an  arrangement  as  this,  to  those  who 
have  many  different  operations  to  perform.     For  a  more  minute 

Fig.  42. 


description,  we  refer  our  readers  to  the  work  from  which  we 
have  taken  the  figure. 

The  reverharatory  furnace  is  rarely  used  except  in  large  ope- 
rations.    In  the  small  way,  a  sort  of  cupola  is  made  by  placing 
a  dome   over  a  wind  or  blast  furnace.     This  differs,  however, 
from  the  true  reverberatory,  in  the  fact  that  the  fuel  surrounds 
the  body   to  be  heated,  whereas,  in  that,  the  entire  heat  is 
derived  from  the  flame  and  its  repercussion  from  the  roof. 
The  cupelling  furnace  has  been  compared  to  the  reverberatory 
furnace.      It   is   a   cupola   containing   a 
Fig.  43.  muffle,  in  which  is  placed  the  material  to 

be  heated.  This  is  a  semicylindrical 
oven,  made  of  refractory  fire-clay,  and 
closed  at  one  end.  On  its  side  are  seve- 
ral openings,  which  allow  the  passage  of 
a  pretty  strong  draught  of  air,  while  they  are  sufiiciently  small 
to  protect  the  assays  from  accidents  arising  from  the  dropping 
in  of  cinders.  In  this  muffle  the  cupels,  hereafter  to  be  de- 
scribed, are  placed. 

There  are  various  forms  of  the  cupelling  furnace.  We  give 
a  cut  of  one  described  by  Morfit,  in  his  Chemical  and  Pharma- 
ceutical 3Ianipulations. 

"  A  A'  is  the  ash-pan,  of  diameter  sufficient  for  the  reception 
of  the  body  of  the  furnace  B  B'.  The  door  C  is  for  the  exit 
of  the  cinders  and  the  ingress  of  the  air.  The  larger  opening, 
D,  in  the  body  of  the  furnace,  is  for  the  introduction  of  the 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


251 


muffle,  and  a  corresponding  one,  D,  opposite,  for  a  prism-shaped 
support  of  baked  clay  for  maintaining  the  muffle  in  a  horizontal 


Fig.  44. 


Fig.  45. 


position.  The  mouth-piece,  supported  by  a  small  platform, 
affords  the  facility  of  admitting  or  preventing  the  access  of  air 
to  the  interior  of  the  muffle. 

"  In  the  part  of  the  dome  E,  is  a  door  for  the  introduction  of 
fuel.  The  two  openings,  e  e,  are  for  the  introduction  of  a  poker 
to  arrange  the  fire. 

"  At  the  top  of  the  furnace  is  a  dome  G  G,  to  which  is 
adapted  a  sheet-iron  pipe  for  increasing  the  draught. 

"  A  sliding  door  H,  and  a  small  circular  gallery  i  i,  as  a  sup- 
port for  heated  coals,  afford  additional  means  of  increasing  the 
draught." 

The  position  of  the  muffle,  with  the  cupola  in  it,  is  seen  in  the 
section.     From   this   arrangement,  it   will   be   perceived   it  is 


252   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

equally  heated  above,  below,  and  at  the  sides,  since  the  fuel 
entirely  surrounds  it. 

The  common  furnace  for  baking  incorruptible  artificial  teeth 

Fig.  46. 


A  muffle  furnace. — a.  Collar  for  sraoko-pipe.  6.  The  opening  through  which  the  fuel  is  intro- 
duced, c.  The  muffle-door.  d.  The  ash-pit  door.  e.  Stopper  for  the  opening  6.  /.  Stopper  for 
closing  the  opening  to  the  muffle,  g.  Stopper  for  the  opening  to  the  ash-pit.  h.  Muffle,  i.  Stop- 
per with  platina  wire  and  test.   j.  Slide. 

is  constructed  on  precisely  the  same  principles  as  the  cupelling 
furnace.  Some  modifications,  however,  are  made  in  the  accom- 
panying furniture.  Thus,  the  muffle  is  fixed,  and  a  slide  is  pro- 
vided for  the  introduction  of  the  paste.  The  mufiie  is  closed 
with  a  door,  having  in  its  centre  a  hole,  which  is  closed  by  a 
fire-clay  plug.  In  this  is  sometimes  inserted  a  platina  wire,  the 
extremity  of  which  carries  a  portion  of  the  paste  of  which  the 
teeth  have  been  carved.  By  withdrawing  this,  from  time  to 
time,  the  progress  of  the  baking  can  be  accurately  ascertained. 
Blast  Furnaces. — The  construction  of  the  blast  furnace  is  as 
various  as  that  of  the  reverberatory.  Many  of  them  are  simple 
cylinders ;  some  are  inverted  and  truncated  cones,  others  double 
hollow  cones  applied  base  to  base. 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  253 

A  simple  and  extremely  powei'ful  furnace  of  this  kind,  for 
laboratory  use,  may  be  made  of  two  blue-pots,  or  black-lead 
crucibles.  The  larger  of  these  is  eighteen  inches  high,  and 
thirteen  in  external  diameter  at  the  top.  Into  this  a  smaller 
pot,  of  seven  and  a  half  inches  external  diameter,  with  its  bot- 
tom cut  away  to  make  an  opening  of  five  inches,  is  introduced. 
This  rests,  by  its  outer  edge,  on  the  bottom  of  the  larger  pot, 
the  tops  of  the  two  being  level.  The  interval  between  them  is 
filled  up  with  pounded  glass  pots,  to  which  enough  water  has 
been  added  to  moisten  the  powder.  A  grate  is  then  dropped 
into  the  inner  pot,  the  space  below  it  constituting  the  air-cham- 
ber, that  above  it  the  body  of  the  furnace.  Finally,  a  conical 
hole,  one  inch  and  a  half  in  diameter,  is  cut  into  the  outer  pot, 
opening  into  the  air-chamber.  It  serves  for  the  introduction  of 
the  nozzle  of  the  bellows. 

With  this  simple  furnace,  not  only  can  pure  iron  be  fused  in 
from  10  to  15  minutes,  but  rhodium  can  be  melted,  and,  ac- 
cording to  Faraday,  platinum  run  together.  All  sorts  of  cruci- 
bles are  destroyed  by  it,  softening,  fusing,  and  becoming  frothy, 
so  that  the  want  of  vessels  capable  of  resisting  its  heat  has 
limited  its  application. 

The  opening  into  which  the  nozzle  of  the  bellows  is  intro- 
duced is  called  the  tuyere,  and  is  usually  so  closed  with  lute  as 
to  admit  no  air  between  its  sides  and  the  blast-pipe.  The 
Messrs.  Barron,  however,  have,  within  the  last  two  or  three 
years,  patented  a  furnace,  which  they  claim  to  be  a  very  great 
improvement.  In  it  the  blast  passes  into  a  wide  tuyere,  a  con- 
siderable space  being  left  between  the  nozzle  of  the  bellows  and 
the  sides  of  the  blast-hole.  They  think  that  a 
greater  blast,  and  consequently  a  more  power-  ^^"-  ^^■ 

ful  heat  can  be  obtained  in  this  way  than  by 
the  ordinary  method.  The  author  attempted 
to  use  one  of  these  furnaces,  as  a  means  of 
making  a  more  expeditious  dry  assay  of  metals.  He  cannot, 
however,  say  that  he  saw  any  particular  advantage  in  them. 
The  failure  may  have  been  due  in  part  to  the  bad  construction 
of  the  furnace,  and  not  to  any  error  in  the  principle  itself. 
There  was  no  provision  for  the  equal  diffusion  of  the  draught,  so 


254   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

that  the  crucible  was  irregularly  heated,  and  the  fire  became 
hollow  on  one  side  from  the  rapidity  of  the  combustion,  while 
on  the  other  it  burned  very  slowly.  This,  it  is  not  necessary  to 
say,  is  a  fatal  defect  in  a  blast  furnace  for  chemical  purposes. 

CRUCIBLES. 

A  crucible  is  a  very  refractory  vessel,  in  which  substances  are 
placed,  in  order  to  be  raised  to  a  high  heat,  whether  for  purposes 
of  fusion  or  of  simple  ignition.  The  materials  of  which  they  are 
made  are  wrought-iron,  platinum,  plumbago,  clay,  and  certain 
admixtures  to  be  presently  described. 

We  shall  hereafter  speak  of  those  finer  varieties  of  clay,  which 
are  used  in  the  manufacture  of  porcelain.  At  present,  a  de- 
scription of  the  qualities  and  composition  of  refractory  clays 
employed  in  the  manufacture  of  articles  designed  to  resist  high 
furnace  heats,  will  form  a  suitable  introduction  to  an  account  of 
the  properties  of  crucibles. 

When  perfectly  pure,  clay  is  infusible  at  the  highest  heat  of  a 
blast,  though  it  may  soften  and  become  lustrous,  showing  that  a 
change  resembling  fusion  is  possible.  There  are,  however,  very 
few  pure  clays.  Those  from  which  the  workman  has  to  choose 
his  materials,  are  all  contaminated  with  foreign  admixtures,  some 
of  which  exert  a  most  unfavorable  influence  over  the  fusibility  of 
the  clay.  The  most  common  impurities  are  oxide  of  iron,  iron 
pyrites,  limestone,  graphite,  and  various  organic  and  bituminous 
matters. 

The  greater  the  number  of  these  ingredients,  the  more  fusible 
will  be  the  compound.  Thus  a  clay  which  is  mixed  with  a  defi- 
nite quantity  of  lime  is  less  fusible  than  another  containing 
magnesia  and  lime,  though  the  two  earths  together  weigh  no 
more  than  the  lime  alone.  The  most  refractory  of  the  pure 
clays  are  those  which  contain  most  silica.  Rotten-stone,  which 
contains  so  much  silica  that  it  cannot  be  called  a  clay,  is  the 
most  infusible  of  the  aluminous  compounds. 

It  is  not,  however,  only  infusibility  which  is  to  be  considered 
in  the  selection  of  a  fire-clay.     Many  clays,  which  leave  nothing 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


255 


to  desire,  as  to  this  point,  are  nevertheless  liable  to  contract  or 
expand  too  strongly,  so  as  to  split  and  fly. 

It  is,  therefore,  necessary  to  select  a  clay  more  or  less  mingled 
with  silicious  sand,  or  to  introduce  some  other  material,  which, 
without  increasing  the  fusibility  of  the  clay,  diminishes  this  pro- 
perty of  too  rapid  contraction. 

According  to  Wurzer,  the  composition  of  the  clay  and  sand 
of  which  the  Hessian  crucibles  are  made,  is  as  follows  : — 


Clay. 

Sand. 

Silica 

10.1 

95.6 

Alumina     ..... 

65.4 

2.1 

Oxides  of  iron  and  manganese 

1.2 

1.5 

Lime 

0.3 

0.8 

Water 

23.0 

— 

100.0 


100.0 


An  idea  of  the  proper  composition  of  clays  for  different  pur- 
poses may  be  obtained  by  a  comparison  of  the  two  following 
tables.  The  first  is  a  series  of  analyses,  made  by  Dr.  Rich- 
ardson, of  clays  taken  from  the  neighborhood  of  Newcastle-upon- 
Tyne,  where  an  extensive  trade  in  fire-bricks  and  gas-retorts  is 
carried  on.  The  clay  for  these  purposes  need  not  be  so  fine  nor  so 
refractory  as  that  out  of  which  crucibles  and  glass  pots  are  to  be 
made.  These  being  thinner,  require  a  very  refractory  mate- 
rial. The  second  table  consists  of  analyses,  by  Berthier  and 
Salvetat,  of  the  most  celebrated  fire-clays  employed  in  the  con- 
struction of  these  vessels. 


Table  I. 


1. 

2. 

3. 

4.        i        5. 

6. 

7. 

Silica 

Alumina       .... 
Oxide  of  iron    .     .     . 

Lime 

Magnesia      .... 
Water  and  organic 
matter      .... 

51.10 

31.35 

4.63 

1.46 

1.54 

10.47 

47.55 

29..50 
9.13 
1.34 
0.71 

12.01 

48.55 

30.25 

4.06 

1.66 

1.91 

10.67 

51.11 

30.40 
4.91  \ 
1.76/ 

trace 

12.29 

71.28 
17.75 

2.43 -> 

2.30  J 

6.94 

83.29 
8.10 
1.88 

2.99  1 
3.64 

69.25 

17.90 

2.97 

1.80 

7.58 

256      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


Table  II. 


Gross  Almerode. 

Beaufave.depart- 

Brierlv  Hill,  near 

Schicrdorf, 

niL-nt  ties 

Stourbridge. 

near  Passau. 

Dried  at  212°. 

Ardennes . 

Berthier. 

Salvetat. 

Berthier. 

Berthier. 

Salvetat. 

Salvetat. 

Silica        .... 

46.5 

47.50 

52.0 

63.7 

45.25 

45.79 

Alumina       .     .     . 

34.9 

34.37 

27.0 

20.7 

28.77 

28.10 

Oxide  of  iron  .     . 

3.0 

1.24 

2.0 

4.0 

7.72 

6.55 

Lime       .... 

— 

0.50 

— 

— 

0.47 

2.00 

Magnesia     .     .     . 

— 

1.00 

— 

— 

— 

— 

Alkalies        .     .     . 

— 

trace 

— 

— 

— 

— 

Hygrometric  water 

— 

0.43 

— 

— 

— 

0.50 

Combined  water    . 

15.2 

14.00 

19.0 

10.3 

17.34 

16.50 

Having  thus  examined  the  composition  of  the  clay,  the  next 
thing  is  to  examine  the  quality  of  the  crucibles  made  from  it. 
It  is  required  in  crucibles :  First,  that  they  should  be  able  to 
resist  great  changes  of  temperature  without  breaking;  secondly, 
that  they  should  be  infusible;  thirdly,  that  they  should  not  be 
attacked  by  the  substances  fused  in  them ;  and,  lastly,  that  they 
should  be  impermeable  to  both  liquids  and  gases.  Novr,  it  is 
impossible  to  fulfil  all  these  indications,  by  any  material  or  com- 
bination of  materials,  known  as  yet  to  the  manufacturers  of 
these  vessels.  Crucibles  are  therefore  made  to  fulfil  one  or 
more  of  them,  so  that  the  operator  can  select  the  variety  spe- 
cially adapted  to  his  wants  in  any  given  case. 

To  furnish  a  crucible  which  will  bear  sudden  changes  of  tem- 
perature without  breaking,  it  is  necessary,  as  has  already  been 
stated,  to  mix  with  the  clay  certain  substances  called  cements, 
which  are  infusible  of  themselves.  Sand,  flint,  fragments  of  old 
crucibles,  black-lead,  and  coke  are  used  for  this  purpose.  The 
materials  selected  and  the  fineness  of  the  powder  to  which  they 
are  reduced,  depend  entirely  upon  the  purpose  for  which  they 
are  required. 

We  have  already  spoken  of  the  refractory  character  of  pure 
clays  free  from  the  metallic  oxides  and  alkaline  earths.  It  has 
also  been  stated  that  they  nevertheless  soften  in  a  high  heat,  so 
that  in  a  wind  furnace  crucibles  made  of  pure  clay  soften  suffi- 
ciently to  fall  into  a  shapeless  mass.     To  obviate  this,  pounded 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


257 


coke  or  black  lead  is  mixed  with  the  clay.  -This,  being  absolutely 
infusible,  resists  the  action  of  the  fire,  and  furnishes  a  sort  of 
skeleton  to  hold  up  the  earthy  portions  of  the  vessel.  Some 
judgment  is  required  to  mix  it  properly  with  the  clay,  for  should 
the  carbonaceous  materials  be  in  too  gross  powder  or  too  large 
quantity,  it  will  burn  out  and  the  crucible  will  crumble. 

The  more  compact  a  crucible  is,  the  more  will  it  resist  the 
action  of  corrosive  agents.  The  materials  of  which  it  is  com- 
posed, and  the  substances  melted  in  it,  will  also  influence  its 
fusibility.  The  oxides  and  fusible  silicates  attack  all  crucibles. 
The  alkalies  and  alkaline  earths  are  sure  to  destroy  clay  cru- 
cibles. They  wear  them  away  layer  by  layer,  till  finally  the 
vessels  become  so  thin  as  to  give  way  to  the  pressure  of  the 
molten  mass  within  them. 

Everything  else  being  equal,  that  crucible  will  be  most  imper- 
meable which  has  fewest  pores  in  it.  None  of  the  earthen 
crucibles  are  entirely  impermeable,  unless  they  have  been  baked 
at  a  heat  high  enough  to  glaze  them.  It  is  customary  to  coat 
these  vessels  with  Willis's  lute,  which  is  a  mixture  of  borax  and 
lime,  when  it  is  desirable  that  they  should  be  impermeable. 

Composition  of  Crucibles. — Berthier's  analysis  of  difi"erent 
varieties  of  crucibles  is  given  in  the  following  table  : — 


Hessian  crucibles  from  Gross  Aliuerode 
French  crucibles  from  Paris      .     .     .     . 

"  "  Beaufoy       .     . 

"              "          St.    Etienne    for 
cast-steel     . 
Englisli  crucibles  for  cast-steel       .     .     . 
Glass  pots  fi'om  Nemours 

'•  Bohemia 


Silica. 

70.9 
64.6 
72.3 

71.0 

65.2 
67.4 
68.0 


Alumina.  I  Oxide  of  iron. 


24.8 
34.4 
19.5 

23.0 
25.0 
32.0 
29.0 


3.8 
1.0 
3.9 

4.0 
7.2 

0.8 


0.5 


Examination  of  Crucibles. — To  determine  whether  a  crucible 
will  bear  great  and  sudden  changes  of  temperature  without 
breaking,  it  is  put  into  a  heated  furnace,  raised  to  a  reddish 
white  heat,  and  then  withdrawn  and  subjected  to  the  blast  of  a 
bellows.  If  it  stand  this,  it  is  heated  to  whiteness,  and  then 
plunged  into  cold  water.  The  best  crucibles  are  unaffected  by 
these  tests. 
17 


258      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

To  determine  its  fusibility,  a  piece  is  broken  off,  taking  care 
that  it  shall  have  sharp  angles,  and  then  heated  to  whiteness  in 
a  crucible  lined  with  charcoal.  If  the  edges  become  rounded 
or  translucent,  the  test-piece  is  fusible. 

The  liability  to  be  attacked  by  metallic  oxides  is  commonly 
ascertained  by  fusing  litharge  in  the  crucible  to  be  tested.  The 
longer  it  retains  this  powerfully  corrosive  oxide  the  better  it  is. 

Two  crucibles  are  easily  compared  as  to  their  permeability, 
by  filling  them  with  water,  and  ascertaining  how  long  it  takes 
for  each  of  them  to  become  damp  on  the  outside. 

Clay  Crucibles. — The  Hessian  crucibles  are  more  frequently 
used  than  any  others  for  rough  fusions,  for  which  they  answer 
very  well.  They  are,  however,  very  easily  attacked  by  many 
of  the  oxides  and  the  alkalies.  In  a  coke-fire  they  are  very 
liable  to  fuse,  if  heated  highly  and  kept  too  long  exposed  to  the 
action  of  the  earths  and  oxides  of  the  fuel.  They  are  accused 
of  being  fragile  when  quickly  heated,  but  I  have  never  had 
reason  to  make  this  complaint  of  good  Hessian  crucibles. 

The  London  crucibles  are  very  refractory.  Beaufaye's  French 
crucibles  are  still  better ;  they  bear  changes  of  temperature 
well,  and  resist  the  corrosive  action  of  the  salts  and  oxides. 

Anstey's  crucibles  are  made  of  two  parts  of  Stourbridge  clay 
and  one  of  the  hardest  gas-coke.  They  are  heated  carefully 
before  the  matter  to  be  fused  is  introduced  into  them.  If  not 
allowed  to  cool,  they  will  bear  from  14  to  18  meltings  of  cast- 
iron.  Pots  made  of  8  parts  of  Stourbridge  clay  and  cement,  5 
of  coke,  and  4  of  graphite,  have  been  found  to  stand  23  meltings 
of  76  pounds  of  iron  each. 

Black-lead  crucibles  must  not  be  used  for  fusing  salts,  as  they 
are  permeated  by  them  ;  nor  for  metallic  oxides,  as  they  reduce 
them,  and  are  gradually  destroyed  by  them.  They  are  valuable 
for  fusing  the  pure  metals,  as  they  are  extremely  infusible. 
They  are  made  of  2  parts  of  graphite  and  1  of  fire-clay. 

Porcelain  crucibles  are  used  for  igniting  oxides,  for  fusions 
of  substances  requiring  a  moderate  heat,  and  for  sulphuration. 
The  French  are  better  than  the  Berlin,  as  they  are  thinner,  and 
not  so  apt  to  crack. 

Iron  crucibles  are  used  for  fusing  silicates  and  a  variety  of 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  259 

salts.  They  should  be  coated  ^iih  clay,  to  preserve  them  from 
oxidation. 

Silver  crucibles  are  only  employed  for  the  fusion  of  potassa 
and  soda,  and  the  preparation  of  caustic  baryta  from  the  nitrate. 

Platinum  crucibles  are  indispensable  to  the  analytical  chemist, 
though  not  often  used  by  the  artisan  or  the  manufacturing 
metallurgist. 

CUPELS. 

These  are  small  shallow  vessels,  flat  at  the  bottom  and  con- 
cave on  their  upper  surface.  They  are  usually  made  of  bone- 
ash. 

The  bones  are  calcined  in  an  open  crucible  to  perfect  white- 
ness.    They  are  then  reduced  to  a  powder,  which  is  repeatedly 

Fig.  48. 


and  thoroughly  washed  in  clear  water,  dried,  and  sifted.     This 

is  now  made  into  a  paste  with  water,  in  wlmh  a  very  small 

quantity  of  carbonate  of  potash  has  been  dissolved,  or  with 

beer.    Mitchell  uses  the  latter  in  the  proportion  of  half  a  pound 

to  4  pounds  of  bone-ash.     To  make  the  cupel  from  this  paste,  a 

mould,  consisting  of  a  ring  and  pestle,  must  be  used. 

The  ring  is  to  be  filled  with  the  composition ;  the        -^^S-  49. 

pestle  is  then  to  be  introduced,  pressed  down  with 

the  hand,  and  finally  driven  home  with  a  mallet.    It 

is  then  turned  lightly  round,  to  smooth  the  inside 

of  the  cupel,  and  withdrawn.    The  cupel  is  removed 

by  tapping  gently  on  its  base,  dried  cautiously  on  a 

stove,  and  then  ignited  in  a  muffle,  to  drive  ofi"  all 

moisture. 

Care  must  be  taken  that  the  powder  of  which  the  cupel  is 
made  is  neither  too  fine  nor  too  coarse ;  neither  too  wet  nor  too 
dry.  It  should  be  compressed  with  a  certain  degree  of  force. 
Should  the  powder  be  too  coarse,  and  only  slightly  moistened 
and  compressed,   the   cupel  will  be  porous,  break  easily,  and 


260      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

allow  the  metal  to  pass  through  it  in  small  globules.  Should  it 
be  too  fine,  too  wet,  and  too  strongly  compressed,  the  cupels  are 
too  solid,  cause  much  delay,  and  demand  a  very  high  tempera- 
ture for  the  completion  of  the  cupellation. 

The  operation  of  cupellation  will  be  described  under  the  head 
of  Metallurgy  of  the  Alloys  of  Silver,  so  that  it  will  not  be 
necessary  to  say  anything  about  it  in  this  place. 

LUTES. 

The  term  lute  is  derived  from  lutum,  mud,  and  is  used  to  ex- 
press any  substance  employed  for  closing  the  joints  of  a  chemical 
apparatus.  The  only  lutes  with  which  we  have  any  concern  at 
present,  are  the  fire-lutes.  These  are  used  to  secure  the  joints 
of  apparatus  subjected  to  high  furnace-heats. 

Parker  s  fire-lute  is  composed  of  clean  clay  2  parts,  sharp- 
washed  sand  8  parts,  horsedung  1  part.  These  are  intimately 
mixed,  and  afterwards  thoroughly  tempered. 

Watts' s  fire-lute  is  made  of  finely  powdered  porcelain  clay, 
mixed  to  the  consistence  of  thick  paint,  with  a  solution  of  borax, 
containing  2  ouftes  of  borax  to  the  pint  of  water. 

Faraday  s  lute  is  made  of  the  best  Stourbridge  clay,  worked 
into  a  paste,  and  beaten  till  it  is  perfectly  ductile  and  uniform. 
It  is  then  flattened  out  into  a  cake,  of  such  a  size  and  shape  as 
shall  be  most  easily  applied  to  the  vessel  to  be  coated.  If  this 
be  a  retort,  it  should  be  placed  in  the  middle  of  a  cake,  which 
should  be  raised  upon  all  sides,  and  gradually  moulded  and  ap- 
plied to  the  glass ;  if  it  be  a  tube,  it  should  be  laid  upon  one 
edge  of  the  plate,  and  applied  by  rolling  the  tube  forward.  The 
surface  to  be  coated  should  always  be  rubbed  with  a  piece  of 
the  lute  dipped  in  water,  for  the  purpose  of  slightly  moistening 
it  and  leaving  a  little  of  the  earth  on  it.  The  lute  should  be 
pressed  down  so  carefully  as  to  exclude  all  air-bubbles,  and  the 
greatest  care  should  be  taken  to  join  the  edges  properly,  for 
which  purpose  they  should  be  made  thin  by  pressure,  and  also 
somewhat  irregular  in  form. 

The  vessels,  thus  luted,  should  be  placed  in  a  warm  situation. 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  261 

and  very  gradually  dried,  being  moved  from  time  to  time,  so  as 
to  prevent  irregularity. 

The  introduction  of  fibrous  substances,  so  as  to  increase  the 
tenacity  by  mechanical  means,  has  been  practised.  Of  these, 
horsedung,  chopped  hay  and  straw,  horse  and  cow  hair,  and 
tow  cut  short,  are  most  frequently  employed.  When  used,  they 
should  be  added  in  small  quantity,  and  the  mixture  should  con- 
tain more  water  and  be  more  thoroughly  and  carefully  mixed. 
It  is  best  to  add  the  fibrous  substance  to  the  dry  clay,  and  to 
stir  with  a  fork  or  pointed  stick  whilst  the  water  is  poured  in, 
so  as  to  obviate  the  necessity  of  using  a  great  quantity  of  water. 
It  ought  to  be  as  dry  as  possible,  consistently  with  facility  of 
working  it.  The  wetter  it  is,  the  more  liable  it  is  to  crack  in 
drying. 

Willis's  cement,  already  spoken  of,  is  made  by  dissolving  one 
ounce  of  borax  in  half  a  pint  of  boiling  water,  and  adding 
slaked  lime  enough  to  make  a  paste.  This  is  to  be  spread  over 
the  vessel  with  a  brush,  and  when  it  is  dry,  a  coating  of  slaked 
lime  and  linseed  oil  is  to  be  applied.  It  will  dry  in  a  day  or 
two,  and  be  fit  for  use. 

FUEL. 

The  operations  which  we  shall  describe  require,  all  of  them, 
a  very  high  temperature,  which  can  only  be  obtained  by  the 
combination  of  oxygen  with  combustible  substances.  These 
combustioles  are  what  we  term  fuel.  There  are  some  substances 
that  are  used  in  the  small  way,  which  properly  come  under  this 
head,  though  not  commonly  known  by  that  name.  These  are 
alcohol,  wood-spirit,  and  the  oils  which  are  used  in  lamps  for 
blowpipe  purposes. 

We  have  already  spoken  of  these  under  the  head  of  blow- 
pipe operations.  It  is  only  necessary  to  compare  their  heating 
powers.  Alcohol  is  the  cleanest  but  weakest  of  the  three. 
Pyroxylic  spirit,  which  contains  more  carbon,  gives  a  hotter 
flame,  and  oil  is  the  hottest  of  the  three. 

Thus,  one  pound  of  common  alcohol  will,  during  its  combus- 


262      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

tion,  raise  52.6  pounds  of  water  from  0°  to  212°,  or  will  evapo- 
rate 9.56  pounds  of  boiling  water ;  while  oil^  wax,  or  tallow  will 
heat  78  pounds  of  water  from  0°  to  212°,  and  evaporate  14.18 
pounds  of  boiling  water.  Carburetted  hydrogen  gas  will  heat 
76  pounds  of  water  from  0°  to  212°,  and  will  evaporate  13.81 
pounds  of  boiling  water. 

The  fuels  used  in  furnaces  are  wood,  coal,  charcoal,  and  coke. 

Wood. — This  fuel  is  often  employed  in  furnaces  wheii  a  quick 
heat  is  desired.  The  amount  of  heat  it  yields  will  be  considered 
when  we  speak  of  the  relative  value  of  different  sorts  of  fuel. 

Wood  is  composed  of  woody  fibre,  the  constituents  of  the  sap 
and  water.  The  first,  or  lignin,  is  a  compound  of  hydrogen, 
carbon,  and  oxygen,  according  to  Prout,  in  the  proportions 
Cj2HgOg.  Payen,  however,  divides  it  into  two  substances,  cel- 
lulose, CjjHjqOio  ;  and  lignin,  C3jH2^02o.  The  first  of  these  con- 
stitutes the  wall  of  the  cells,  and  the  second  their  contents. 
The  earthy  matters  found  in  the  ashes  are  contained  in  the  sap, 
which  also  holds  in  solution  the  peculiar  organic  principles  of 
the  plant.  The  relative  proportions  of  these  ingredients  have 
been  found  to  vary  with  the  season  in  which  the  wood  has  been 
cut.  During  the  period  of  active  growth  they  contain  more 
water  and  sap  than  during  the  winter.  The  different  parts  of 
the  plant  also  differ  in  this  respect.  Thus,  the  small  shoots  and 
twigs  yield  a  larger  percentage  of  water  than  the  more  solid 
stems. 

Schubler  and  Hartig  examined  many  varieties  of  wood,  and 
found  that  the  quantity  of  water  varied  from  less  than  one-fifth 
to  more  than  one-half  of  their  weight.  Thus,  hornbeam  con- 
tained 18.6,  horse-chestnut  38.2,  and  black  poplar  51.8^  of 
water.  According  to  Marcus  Bull's  experiments,  green  hickory 
loses  87|,  white  oak  41,  and  soft  maple  38^  by  thorough 
drying. 

Exposed  to  the  air,  wood  loses  water,  and  then  it  is  said  to 
be  air-dried.  It  still,  however,  retains  a  notable  quantity  of 
water,  as  will  be  seen  by  the  following  table  of  some  of  the  re- 
sults of  Count  Rumford,  who  kept  specimens  of  various  air-dried 
woods  at  277°,  till  they  ceased  to  lose  weight : — 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC. 


263 


100  pai 

ts 

of  oak  wood  lost    . 

16.64 

elm 

18.20 

beech 

18.56 

maple 

18.63 

fir 

17.53 

birch 

19.38 

lime 

18.79 

ood,  in 

its 

poplar 
ffreen  sta 

te,  contains  on  an 

averas 

19.55 
!;e  abou 

per  cent,  of  moisture,  and  after  being  air-dried  for  a  year,  from 
20  to  25  per  cent.  According  to  Winkler,  wood  several  years 
old,  kept  in  a  warm  room  for  six  months,  contained  17  per  cent, 
of  water.  Bull  found  that,  after  wood  had  been  thoroughly 
dried,  it  Avould,  in  twelve  months,  absorb  from  the  air  of  a  room 
10  per  cent,  of  water. 

A  moment's  consideration  will  convince  any  one  that  economy 
of  fuel  demands  that  wood  should  be  used  as  dry  as  possible. 
All  the  water  which  is  contained  in  it  must  be  converted  into 
steam  at  the  expense  of  the  fuel.  Green  wood  contains  17§ 
more  water  than  seasoned  wood.  To  convert  this  into  steam, 
6.8  pounds  of  dry  wood  are  required.  Estimating  by  weight, 
therefore,  nearly  one-fourth  of  the  fuel  is  lost.  If  we  estimate 
the  loss  by  measure,  as  the  water  does  not  materially  affect  the 
bulk  of  the  wood,  we  shall  find  that  at  least  10  J*-  is  lost,  by  burn- 
ing green  instead  of  dry  wood. 

Woods  are  usually  divided  into  two  classes,  hard  and  soft, 
names  taken  from  their  resistance  to  edge-tools,  but  answering 
very  well  to  indicate  their  density  and  their  power  of  calorifica- 
tion. Trees  of  the  same  species  vary  in  density  and  hardness, 
according  to  the  situation  in  which  they  are  grown.  Those 
growing  on  thin  soils,  in  an  exposed  situation,  are  harder  and 
denser  than  those  more  sheltered  and  grown  on  richer  land. 

Dry  wood  is  much  lighter  than  water,  but  this  is  due  to  the 
air  contained  in  its  cavities.  When  rasped,  or  filed,  so  as  to 
destroy  the  pores,  and  thus  deprive  it  of  all  but  its  natural 
buoyancy,  the  lightest  wood  is  found  to  be  denser  than  water. 


264   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

By  this  treatment  the  specific  gravities  of  the  following  woods 
is  found  to  be — 

Oak 1.27 

Lime* 1.13 

Fir 1.16 

Beech    .        • 1.29 

Long  immersion  in  water  deprives  wood  of  its  soluble  and  ex- 
tractive matter,  so  that  its  calorifying  powers  are  impaired. 

Different  kinds  of  wood  do  not  differ  very  widely  in  their 
chemical  composition,  except  as  regards  the  inorganic  matters 
contained  in  their  ash.  It  is  remarkable,  however,  that  in  all 
the  varieties  which  have  yet  been  examined,  there  is  a  slight 
excess  of  hydrogen  over  oxygen,  though  in  woody  fibres,  the 
two  elements  are  combined  in  the  proportion  to  form  water. 
Thus,  Schadler  and  Petersen  obtained  results  a  few  of  which 
are  given  below. 

Carbon. 
Pure  woody  fibre  52.65 

Quercus  robur  (oak)  49.43 
Fagus  sylvatica  (beech)  48.53 
Pinus  abies  (fir)  49.95 

The  ashes  of  wood  vary  not  only  with  the  species  examined, 
but  with  the  soil  on  which  it  grows.  Generally,  they  consist  of 
potash,  soda,  lime,  magnesia,  and  iron  combined  with  carbonic, 
silicic,  sulphuric,  and  phosphoric  acids,  together  with  the  chlorides 
of  their  radicals. 

The  amount  of  ash  furnished  by  the  difi"erent  species  varies 
very  much.  Thus  Berthier  found  that  fir  yielded  only  0.0083, 
while  the  linden  or  lime  tree  gave  1.05^  of  ash.  The  diff"erent 
parts  of  the  tree  also  yield  different  quantities  of  ash,  the  bark 
and  leaves  yielding  the  most,  the  branches  less,  and  the  trunk 
least  of  all. 

Turf  and  Peat. — These  are  the  products  of  vegetable  decom- 
position in  low,  moist  places.     Large  quantities  of  water-plants 

*  Tilia  Europosa,  our  common  shade-tree,  the  linden. 


Hydrogen. 

Oxygen. 

5.25 

42.10 

6.07 

44.50 

6.30 

45.17 

6.41 

43.65 

METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  265 

spring  up  on  these  moors  in  the  summer  months,  and  in  winter 
they  die  and  fall  upon  the  ground.  They  undergo  decomposi- 
tion, the  gaseous  matter  escaping,  and  the  greater  portion  of  the 
carbon  and  the  salts  remaining. 

In  turf^  the  decomposition  is  not  so  complete  as  entirely  to 
destroy  the  texture  of  the  plants.  Many  twigs  and  roots  still 
remain  in  it,  and  though  dark-colored,  it  is,  neverthess,  light 
and  porous.  In  2)eat^  all  traces  of  vegetable  form  are  lost,  and 
the  density  of  the  mass  is  very  much  increased. 

The  proportion  of  ash  varies  from  4.61  to  33?-.  The  quan- 
tity of  hydrogen  and  oxygen  is  very  variable.  The  average 
percentage  of  carbon  is  about  57.5. 

Coal. — The  geological  situations  of  coal  are  in  the  tertiary 
and  secondary  fo7'mations  and  in  the  coal  measures,  which  lie 
between  the  new  red  sandstone  and  the  carboniferous  limestone. 

Lignite. — This  is  found  in  tertiary  formations,  and  divisible 
into  several  varieties,  such  as  brown  coal,  bituminous  tvood, 
common  earthy  lignite.  Of  these,  the  broivn  coal  resembles  turf, 
and  loses  about  20  4  of  water  on  thorough  drying,  and  yields 
35  to  40^  of  a  coke  resembling  charcoal.  Bituminous  ivood  is 
softer,  retains  to  a  certain  extent  its  woody  character,  but  is 
dark-brown  or  black,  and  more  nearly  resembles  asphaltum  or 
mineral  pitch  than  the  wood  from  which  it  is  formed.  Common 
ligyiite  resembles  coal  from  the  secondary  foi'mations.  It  is 
usually  black  or  brown,  with  a  compact  structure  and  an  irregular 
fracture.  When  heated  it  gives  off  inflammable  gases,  together 
with  acid  and  tarry  matter  ;  and  the  resulting  coke  usually 
retains  the  form  of  the  fragment  from  which  it  was  produced. 
Earthy  lignites,  as  their  name  implies,  contain  foreign  matters, 
the  principal  of  which  are  clay  and  iron  pyrites. 

In  the  United  States,  the  chief  deposit  of  this  coal  is  near 
Richmond.  The  proportion  of  ash  varies  greatly,  the  earthy 
lignites  of  course  yielding  the  most.  Thus,  lignite  from  Lau- 
bach,  contains  only  0.49g  of  ash,  while  that  of  Meiszner  has 
19.1^.  The  formula  of  lignite  free  from  bitumen  has  been 
stated  at  C33H2jOjg. 

3Iineral  Coal. — In  this  variety  of  coal,  all  traces  of  vegetable 
tissue  have  disappeared,  though  impressions  of  plants  are  always 


266      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

found  among  the  shales  which  cover  the  beds.  There  are  two 
varieties  of  mineral  coal,  the  bituminous  or  pit  coal,  and  an- 
thracite. 

Pit  Coal,  Bituminous  Coal. — This  coal  is  found  in  compact 
masses  or  great  beds  interstratified  with  earthy  matters.  It  is 
black,  sometimes  dull,  but  often  has  a  glassy,  and  sometimes  an 
iridescent  lustre,  and  a  conchoidal  or  hackly  fracture.  The 
black  and  shining  variety  with  a  conchoidal  fracture  is  rich  in 
carbon,  while  that  which  is  dull  and  brown  contains  less  of  that 
element. 

The  physical  characters  of  coal  have  furnished  a  basis  for  the 
classification  of  the  different  varieties.  That  which  is  compact 
and  has  a  resinous  lustre  is  called  pitch  coal.  When  it  has  a 
cubical  fracture,  it  is  called  cubical  or  cherry  coal.  When  it 
melts  and  ngglomerates  in  the  fire,  it  is  termed  caking  coal ; 
and  when  it  can  be  easily  split  in  leaves  parallel  to  the  surface 
of  deposition,  it  is  called  slate  or  splint  coal. 

The  average  specific  gravity  of  bituminous  coal  is  about  1.3. 

Anthracite. — This  is  the  most  solid  and  compact  of  the  coals. 
Its  specific  gravity  varies  from  1.343  to  1.751.  It  forms  thick, 
continuous  beds  of  great  extent.  It  is  black,  ^Yith  a  shining, 
sometimes  almost  metallic  lustre,  with  occasionally  a  brilliant 
iridescence.  Its  fracture  is  more  irregular  than  that  of  pit- coal, 
and  is  usufilly  conchoidal.  It  is  the  hardest  and  toughest  of  all 
the  coals,  kindles  with  more  difficulty,  but  burns  readily  in 
masses,  with  little  flame,  and  throws  out  an  intense  heat. 

The  following  table  of  analyses  by  Regnault  and  Richardson, 
exhibits  the  difference  in  the  chemical  composition  of  coals : — 


Carbon. 

Hydrogen. 

Oxygen  and 
Nitrogen. 

Ash. 

Turf    . 

58.09 

5.93 

31.37 

4.61 

Lignite 

71.71 

4.85 

21.67 

1.77 

Splint  Coal   . 

82.92 

6.49 

10.86 

0.13 

Cannel 

83.75 

5.66 

8.04 

2.55 

Cherry  Coal 

84.84 

5.05 

8.43 

1,68 

Caking  Coal 

87.95 

5.24 

5.41 

1.40 

Anthracite    . 

91.98 

3.92 

3.16 

0.94 

METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  267 

The  influence  of  heat  on  fuel  is,  of  course,  to  decompose  it, 
but  the  products  of  this  decomposition,  when  air  is  excluded  and 
when  it  is  freely  admitted,  differ  very  widely. 

When  air  is  excluded,  as  in  dry  distillation,  the  volatile  and 
combustible  products  of  the  decomposition  may  be  collected. 
Under  the  influence  of  a  high  heat,  hydrogen  and  oxygen  are  of 
course  volatilized,  but  they  do  not  pass  over  as  pure  gases. 
Much  of  the  oxygen  combines  with  the  hydrogen  to  form  water. 
A  portion  of  it  unites  with  the  carbon,  and  still  more  of  it  with 
the  carbo-hydrogens,  formed  from  the  excess  of  hydrogen,  which 
always  exists  in  fuel.  Thus,  we  have  a  series  of  compounds  con- 
tinually varying  with  the  variable  amounts  of  these  three  ele- 
ments. The  permanently  gaseous  products  are  usually  carbo- 
hydrogens  only  ;  but  besides  these,  the  dry  distillation  of  fuels 
affords  acetic  and  other  acids,  'pyroxylic  spirit,  creosote,  tar,  and 
a  very  great  variety  of  substances  allied  to  petroleum,  as  well  as 
such  solids  as  naphthaline  and  paraffine. 

When  air  is  freely  admitted,  however,  these  volatile  products, 
already  at  a  high  temperature,  are  rapidly  consumed  ;  so  that, 
with  the  exception  of  carbon  and  a  few  unconsumed  products  of 
decomposition,  which  go  up  as  soot,  the  whole  combustible  mat- 
ter is  resolved  into  carbonic  acid  and  water. 

These  natural  fuels  are  often  treated  so  as  to  get  a  more  eco- 
nomical fuel  in  a  given  bulk.  Thus  wood,  containing,  as  we 
have  seen,  after  the  most  thorough  drying,  a  large  quantity  of 
water,  must  necessarily  lose  a  great  deal  of  its  calorific  power. 
When,  however,  it  is  converted  into  charcoal,  this  source  of  loss 
is  avoided,  and  a  fuel  is  obtained  of  which  a  given  bulk  is  capa- 
ble of  evolving  a  far  greater  quantity  of  caloric. 

Charcoal. — When  wood  is  ignited,  and  then  excluded  from 
the  air  while  burning,  its  volatile  products  are  driven  off  by  the 
slow  combustion  which  continues  for  a  short  time,  and  its  carbon 
is  left  behind.  Some  of  the  latter,  however,  is  necessarily  lost 
in  consequence  of  its  having  been  consumed  to  furnish  the  heat 
which  has  driven  off  the  volatile  products.  If,  however,  it  be 
heated  at  once  in  a  close  vessel,  these  products  are  driven  off  with- 
out loss  of  carbon.  The  difference  between  the  charcoal  yielded 
by  these  two  processes  is  very  great.     Karsten  found  that  pine, 


268      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

which  gave  only  13.75^  of  charcoal  by  the  process  of  quick- 
charrmg,  yielded  25.95  by  the  slow  process. 

Charcoal  is  commonly  made  by  building  the  wood  into  piles 
of  peculiar  construction,  covered  with  turf,  so  as  to  admit 
only  air  enough  for  a  very  slow  combustion.  At  first,  a  yel- 
low smoke  escapes,  which  contains  the  volatile  products  first 
formed,  mixed  with  much  watery  vapor,  but  gradually  the  color 
of  the  smoke  clianges  to  a  clearer  blue,  showing  that  the  water 
is  nearly  expelled.  At  this  period  the  openings  are  all  closed, 
and  the  wood  is  allowed  to  char. 

This  process  is  liable  to  the  objection  that  it  wastes  the  vola- 
tile products,  Avhich  are  often  very  valuable.  To  obviate  this, 
furnaces  have  been  constructed,  which  are  provided  with  tubes 
and  vessels  to  carry  off  and  condense  these  volatile  substances. 
Some  of  these  furnaces  are,  like  the  charcoal  mounds,  heated 
by  the  wood  itself.  Others  are  cylindrical  ovens  heated  by  an 
external  fire,  or,  after  the  process  commences,  by  the  gas  which 
comes  off  from  the  charring  wood. 

The  average  quantity  of  charcoal  produced  in  mounds  amounts 
to  about  22{5.  The  furnaces  yield  27^,  but  it  requires  about 
5g  to  heat  them,  so  that  the  gain  is  only  represented  by  the  vo- 
latile products  which  have  been  saved. 

The  specific  gravity  of  charcoal  varies  with  that  of  the  wood 
from  which  it  has  been  taken.  Thus,  Knapp  found  that  a  cubic 
foot  of  beech-wood  charcoal  weighed  from  8  to  9  pounds  ;  of 
oak  charcoal,  7  to  8  pounds  ;  of  pine  charcoal,  5.5  to  7  pounds, 
and  of  the  charcoal  from  the  softer  woods,  from  4.5  to  5.5  pounds. 

The  charcoal  obtained  by  these  processes  is  not  absolutely 
pure  carbon,  as  by  heating  them,  about  7  per  cent,  of  volatile 
matter  can  still  be  driven  off. 

Charcoal  is  a  powerful  absorbent.  It  abstracts  a  large  quan- 
tity of  water  from  the  atmosphere,  and  absorbs  gases  with  great 
energy.  Its  strongest  affinity  is  for  ammoniacal  gas,  of  which 
it  absorbs  90^-;  its  weakest  is  for  hydrogen,  of  which  it  only 
absorbs  1.75g. 

There  is  a  point  at  which  the  charring  process  should  stop. 
If  carried  too  far,  loss  will  be  sustained.     Thus,  Berthier  found 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  269 

that  if  a  cubic  foot  of  wood  contains  a  weight  of  combustible 
matter  represented  by  908 — 

1  cubic  foot  charred  during  3  hours  will  contain    883  parts. 
1  «  "4       "  "  904     " 

1  «  "  5       "  "  1133     " 

1  "  "  5|     "  "  1091     " 

1  "  "  6|     "  "  113(3     " 

1  "       mound  charcoal,  will  contain  1069     " 

It  follows,  from  the  above  table,  that  the  process  of  charring 
may  be  advantageously  checked  before  complete  carbonization 
is  attained.  In  France  and  Belgium,  a  great  saving  is  effected 
by  using  wood  thus  imperfectly  charred.  It  is  called  cJiarbon 
roux.  The  objection  to  it  is  that  it  is  very  difficult  to  secure 
anything  like  uniformity  in  the  quality  of  the  article. 

Peat  charcoal  is  often  used  in  Europe.  A  given  weight  of 
lignite  produces  more  charcoal  than  the  same  weight  of  wood, 
for  reasons  which  are  too  manifest  to  need  rehearsing. 

Coke. — Coke  bears  the  same  relation  to  bituminous  coal  that 
charcoal  does  to  wood.  It  generally  contains  more  combustible 
matter  in  the  same  bulk  than  the  coal  from  which  it  has  been 
obtained.  It  should  be  solid  enough  not  to  crush  easily,  and 
should  come  in  tolerably  large  pieces.  Spongy  coke,  easily 
crushed,  is  not  an  economical  fuel. 

Like  charcoal,  coke  is  made  in  heaps  or  in  ovens.  In  this 
country,  most  if  not  all  of  the  coke  which  is  used  is  obtained 
from  gas-houses,  and  as  refuse  from  furnaces  heated  by  bitumi- 
nous coal. 

On  cooling,  good  coke  splits  into  long  prismatic  masses,  not 
unlike  basaltic  columns.  Its  color  is  a  steel-gray,  at  times 
approaching  a  silvery  whiteness,  and  having  now  and  then  a 
metallic  lustre.  Some  varieties  are  iridescent,  an  appearance 
which  is  believed  to  depend  upon  the  presence  of  sulphur.  Like 
charcoal,  coke  absorbs  moisture  from  the  atmosphere.  In  damp 
weather,  this  hygrometric  water  is  sometimes  as  much  as  30  per 
cent.  After  long  exposure  to  moisture,  coke  becomes  soft  and 
friable,  and  becomes  worthless  for  some  of  the  purposes  to  which 
it  has  been  applied. 


270      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Comparative  Value  of  Fuels. — The  different  fuels  which  have 
been  enumerated  vary  very  greatly  in  their  heating  powers. 
Different  methods  have  been  adopted  to  determine  the  calorific 
energy  of  different  sorts  of  fuel.  The  object  is  to  ascertain  the 
amount  of  heat  produced  and  the  time  required  to  generate  it. 
Now,  as  it  is  impossible  to  estimate  the  amount  of  heat  actually 
produced,  the  results  of  the  caloric,  or  its  effects,  or  something 
else  have  been  chosen  as  indicating  as  nearly  as  possible  the 
relative  value  of  fuels. 

The  instrument  by  which  these  effects  are  determined  is  called 
a  calorimeter,  and  the  heat  is  measured  either  by  the  quantity 
of  ice  melted,  or  the  weight  of  water  elevated  to  a  given  tem- 
perature, or  evaporated  by  the  substance  operated  upon.  An- 
other method  is  to  determine  the  period  during  which  an  apart- 
ment may  be  kept  at  a  given  temperature.  It  was  this  latter 
method  which  was  adopted  by  Marcus  Bull,  in  his  admirable 
researches,  a  table  of  the  results  of  which  we  subjoin : — 


METHODS  OF  APPLYING  HEAT,  FURNACES.  ETC. 


271 


White  asli  l^Fraxiniis  Ame- 
ricana)        

Apple- tree  {Pyrus  malus) 

White  beech  [Fagiis  syl- 
vcs(ris) 

Bhick  birch  {Betula  buta) 

White  birch  [Betula popu- 
lifoUa) 

Butternut     [Jiiglans     ca- 
thariica 

Red  cedar  [Juniperus  Vir- 
ginian a)     

American  chestnut  [Cas- 
tanea  vesca')     .     .     .  '  . 

AVild  cherry  [Cerasus  Vir- 
giniana) 

Dogwood  [Cornus florida) 

White  elm  ( Ulmus  Ameri- 
cana)      

Sour  gum  [Nyssa  sylvatica) 

Sweet  gum  \Liquidambar 
styracijiua)      .... 

Shell-bark  hickory  ( Carya 
squamosa)       .... 

Pig-nut    hickory   [Carya 
porcina) 

Red-heart  hickory 

Witch    hazel   [Hamamelis 
Virgin  ica)       .... 

American    holly    [Hex 
opaca) 

American  hornbean  [Car- 
pinus  Americana)     . 

Laurel  (Kalmia  latifolia) 

Hard  maple  [Acer  saccha- 
rinum) 

Soft  maple  [Acer  rubrum) 

Large  magnolia  [llagnolia 
grandijlora)     .... 

Chestnut  white  oak  ( Quer- 
cus  prinos  palusiris) 

White  oak  [Q.  alba)    .     . 

Shell-bark  white  oak  [Q. 
obtusa)       

Scrub  oak  [Q.  catesbsei)   . 

Pin  oak  ( Q.  palusiris) 

Scrub  black  oak  ( Q.  bar- 
risteri)        

Red  oak  [Q.  rubra)     .     . 


.772 
.697 

.72-1 
.097 

.530 


.567 
.565 
.522 


^■6 

n 


.59 
.815 

.580 
.708 

.034 

1.000 


.945; 
.829 

.784 

.602 

.720 
.663 

.644 
.597 

.605 

.885 
.855 

.775 
.747 
.747 


.728 
.728 


3450 
3115 

3230 
3115 

2369 

2534 

2525 

2833 

2668 
3643 

2592 
3142 

2834 

4469 

4241 
3705 

3505 

2091 

3218 
2903 

2878 
2668 

2704 

395-: 
3821 

3464 

3339 
3339 

3254 
3254 


3  °  Tr 

III 

o 

L 

"3 

"3  o 
It 
1° 

S  9  >-. 

■3"S 

o 

2  ° 

li.  ni. 

25.74 

.547 

28.78 

888 

31 

6  40 

25.00 

.445 

23.41 

779 

33 

0  40 

19.62 

.518 

27.26 

035 

23 

r; 

19.40 

.428 

22.52 

004 

27 

0 

19.00 

.364 

19.15 

450 

24 

0 

20.79 

.237 

12.47 

527 

42 

1) 

24.72 

.238 

12.52 

624 

50 

6  40 

25.29 

.379 

19.94 

590 

30 

0  40 

21.70 

.411 

21.63 

579 

27 

6  10 

21.00 

.550 

28.94 

765 

20 

li  10 

24.85 

.357 

18.79 

644 

84 

6  40 

22.10 

.400 

21.05 

696 

33 

6  20 

19.09 

.413 

21.78 

558 

20 

0 

26.22 

.625 

32.89 

1172 

36 

0  40 

25.22 

.637 

33.52 

1070 

32 

0  40 

22.90 

.509 

26.78 

848 

82 

6  30 

21.40 

.868 

19.36 

750 

39 

0  10 

22.77 

.374 

19.68 

013 

31 

6  20 

19.00 

.455 

23.94 

611 

25 

') 

24.02 

.457 

24.05 

712 

30 

0  40 

21.43 

.431 

22.68 

617 

27 

(3  10 

20.04 

.870 

19.47 

551 

28 

6 

21.59 

.400 

21.86 

584 

27 

6  10 

22.70 

.481 

25.31 

900 

36 

6  30 

21.62 

.401 

21.10 

826 

39 

•J  20 

21.50 

.437 

22.99 

745 

32 

0  20 

23.17 

.392 

20.63 

774 

38 

6  30 

22.22 

.430 

22.94 

742 

32 

6  20 

23.80 

.387 

20.30 

774 

38 

(5  30 

22.43 

.400 

21.05 

030 

30 

0  20 

•  00 
54 


272      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


o 

C    O 

"5  & 

"3 
o 

5  = 

1- 

■?=s 

^ 

3  ^ 

^  ^  ^ 

^ 

o 

^■3 

^  "p 

•«-3     • 

■--  -^    \i 

V 

OS 

C    ? 

'i  %.' 

2  ^   ^ 

III 

1 

1-2 

'  o 

Ms 

III 

egg 

"■   7r.   O 

=  §-^ 
•5  =  3 

h.  m. 

Cord. 

Barren  oak  {Q.ferruginea) 

.694 

3102 

22.37 

.447 

23.52 

694 

29 

6  20 

66 

Rock   chestnut    oak    {Q. 

montana) 

.G78 

3030 

20.86 

.430 

22.94 

632 

28 

6 

61 

Yellovr  oak  (  Q.  acuminata) 

.653 

2919 

21.60 

.2'.i5 

15.52 

631 

41 

6  10 

60 

Spanish  oak  {Q.falcata) 

.548 

2499 

22.95 

.362 

19.05 

562 

30 

6  20 

52 

Persimmon  (Z>«o«/^)-os  Vir- 

giniana) 

.711 

3178 

23.44 

.469 

24.68 

745 

30 

6  30 

09 

Yellow  pine,   soft  [Pinus 

variabilis)       .... 

.551 

2463 

23.75 

.333 

17.52 

585 

33 

6  30 

.54 

Jersey  pine  (P.  inops) 

.478 

2137 

24.88 

.385 

20.26 

532 

26 

6  40 

48 

Pitch  pine  (P.  rigida) 

.426 

1904 

26.76 

.298 

15.68 

510 

33 

6  40 

43 

White  pine  (/'.  strobus)    . 

.418 

1868 

24.35 

.293 

10.42 

455 

30 

6  40 

42 

Yellow   poplar  (Lirioden- 

dron  tulip  if  era)    . 

.563 

2516 

21.81 

.383 

20.15 

549 

27 

6  10 

52 

Lombardy  poplar  [Popidus 

dilatata) 

.397 

1774 

25.00 

.245 

12.89 

444 

34 

6  40 

40 

Sassafras  {Laurus  sassa- 

fras)  

.618 

2762 

22.58 

.427 

22.47 

624 

28 

6  20 

59 

Wild  service  (Aronia  ar- 

borca)   

.887 

3964 

22.62 

.594 

31.26 

897 

29 

6  20 

84 

Sycamore  (Platanus  occi- 

dentalis) 

.535 

2391 

23.60 

.374 

19.68 

564 

29 

6  4(1 

52 

Black    walnut    [Juglans 

nigra) 

.681 

3044 

22.56 

.418 

22.00 

687 

31 

6  20 

65 

Swamp     Whortleberry 

^ 

(  Vacciniiim  corymbosum) 

.752 

3361 

23.30 

.505 

26.57 

783 

29 

6  30 

73 

Ton. 

99 

Lehigh  coal 

1.494 

78.61 

13  10 

Lackawanna  coal 

1.400 

73.67 

13  10 

99 

Rhode  Island  coal 

1.438 

75.67 

9  30 

71 

Schuylkill  coal  . 

1.453 

76.46 

13  40 

103 

Susquehanna  coal 

1.373 

72.25 

13  10 

99 

Swatara  coal 

1.459 

76.77 

11  20 

85 

Worcester  coal  . 

2.104 

110.71 

7  50 

59 

100  bu. 

Cani^el  coal  .     . 

1.240 

62.25 

10  30 

230 

Liverpool  coal    . 

1.331 

70.04 

9  10 

215 

Newcastle  coal  . 

1.204 

63.35 

9  20 

198 

Scotch  coal   .     . 

1.140 

59.99 

9  30 

191 

Karthaus  coal    . 

1.263 

66.46 

9  20 

208 

Richmond  coal  . 

1.246 

65.56 

9  20 

205 

Stony  Creek  coal 

1.396 

73.46 

9  50 

243 

Hickory  charcoal 

.625 

32.80 

15 

166 

Maple  charcoal 

.431 

22.68 

15 

114 

Oak  charcoal     . 

.401 

21.10 

15 

106 

Pine  charcoal    . 

.285 

15.00 

15 

75 

Coke    .... 

.557 

20.31 

12  50 

126 

Composition,  2  parts  Le- 

high, 1  charcoal,  1  clay, 

by  weight       .... 

13  20 

METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  273 

Another  very  ingenious  method  has  been  suggested  by  Ber- 
thier.  He  bases  his  process  upon  a  discovery  of  Welter,  that 
the  amount  of  heat  produced  by  burning  bodies  is  in  direct  pro- 
portion to  the  quantity  of  oxygen  required  to  effect  their  com- 
bustion. He  mixes  intimately  with  litharge  a  known  weight  of 
the  substance  in  fine  powder,  and  heats  it  in  a  closed  crucible. 
The  oxygen  of  the  litharge  combines  with  the  combustible,  and 
lead  sinks  to  the  bottom  in  a  button.  A  comparison  of  the 
weight  of  one  button  with  that  of  another  affords  an  estimate  of 
the  value  of  the  tested  articles  as  fuel.  Carbon,  which,  accord- 
ing to  Despretz,  affords  34.5  parts  of  metallic  lead,  is  selected 
as  the  standard  of  comparison.  It  must  be  borne  in  mind,  in 
these  investigations,  that  the  reducing  power  of  hydrogen  is 
more  than  three  times  as  great  as  that  of  carbon.  Forgetful- 
ness  of  this  will  lead  to  grave  errors  in  the  estimation  of  the 
results  obtained. 

lire,  whose  results  differ  very  widely  from  Berthier's,  and 
from  those  of  other  chemists  who  have  adopted  this  method, 
expresses  a  total  want  of  confidence  in  it.  He  found  that  1  part 
of  charcoal  produced  60.3  parts  of  lead  ;  whereas,  according  to 
Berthier  and  Despretz,  but  34.5  were  possible. 

It  may  be  that,  in  these  experiments  of  lire's,  some  sulphuret 
of  iron  was  present,  which  would  in  part  account  for  this  great 
difference. 

It  must  be  borne  in  mind  that  the  theoretical  results  obtained 
by  these  processes  differ  somewhat  from  those  actually  arrived 
at  in  practice.  This  depends  upon  a  variety  of  circumstances, 
the  arrangements  of  the  furnaces,  the  extent  of  the  surface  to 
be  heated,  the  manner  in  which  the  heat  is  applied,  &c. 

Time  is  a  very  important  element  in  the  estimation  of  the 
effect  of  fuel.  For  some  purposes  a  rapid  heat  is  desirable.  The 
lighter  woods,  which  contain  much  hydrogen,  will  be  applicable 
to  these.  As  a  general  thing,  however,  the  more  slowly  burning 
fuels  are  the  best,  because  it  takes  time  for  the  substances  to  be 
heated  to  absorb  the  necessary  amount  of  caloric. 

The  freedom  of  the  circulation  of  air  is  another  most  import- 
ant element  of  the  heating  powers  of  a  fuel.  A  full  supply  of 
oxygen  is  necessary  for  the  perfect  evolution  of  the  entire  amount 
18 


274      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  heat  of  which  any  fuel  is  capable.  Any  defect  in  the  bars  of 
the  furnace,  or  in  the  structure  of  a  chimney,  will  consequently 
materially  interfere  with  the  perfect  combustion  of  the  fuel. 

The  size  of  the  pieces  introduced  into  the  furnace  will,  for 
the  same  reason,  affect  the  combustion.  If  they  are  too  large, 
they  will  absorb  too  much  heat,  and  will  consequently  lose  caloric. 
If  too  small,  they  will  burn  too  rapidly.  When,  however,  they 
are  extremely  small,  they  fall  together  and  choke  up  the  draught, 
so  that  the  mass  only  smoulders,  like  tan  in  a  fireplace. 

Practically,  for  the  purposes  of  the  chemist,  the  best  fuel  is 
charcoal  or  coke,  or  a  mixture  of  the  two.  The  ash  of  charcoal 
being  infusible,  it  passes  through  the  bars  of  the  grate  as  a  white 
powder.  Should  potash,  however,  be  in  large  excess,  it  corrodes 
the  bricks,  by  forming  with  them  a  silicate  of  potash,  which  runs 
down  the  walls  and  chokes  the  bars.  In  small  quantities,  this 
action  is  beneficial,  as  it  furnishes  a  protective  varnish,  and 
unites  the  bricks  and  lutes,  by  forming  a  sort  of  cement,  which 
intimately  combines  with  them. 

Coke  contains  a  very  variable  amount  of  ash,  which  is  com- 
posed chiefly  of  oxide  of  iron  and  clay.  The  latter  is  not  fusible 
by  itself,  but  may  soften.  When  pure,  it  forms  a  harmless  slag, 
which  injures  neither  the  furnace  nor  the  crucibles.  Usually, 
however,  the  oxide  of  iron  predominates.  In  this  case  the  ash 
is  very  injurious,  for  it  is  reduced  to  a  protoxide,  which  is  not 
only  fusible,  but  powerfully  corrosive  to  all  argillaceous  matters, 
so  that  both  the  crucibles  and  the  furnaces  suffer. 

Coal,  of  course,  is  liable  to  all  the  objections  which  can  be 
urged  against  coke,  and  the  presence  of  sulphur  in  it  increases 
the  difficulties.  Bituminous  coal  should  never  be  used  in  cru- 
cible operations,  because  it  swells  so  as  to  be  very  troublesome. 
Anthracite  may  be  used  if  carefully  selected.  It  is  unnecessary 
to  say  that  it  must  be  perfectly  free  from  slate,  must  yield  an 
infusible  ash,  and  be  as  clean  as  possible.  It  is,  however,  as 
far  as  the  author's  experience  goes,  decidedly  inferior  to  either 
coke  or  charcoal.  Some  of  the  softer  varieties  of  it  are  very 
bad,  so  imperfectly  have  they  been  cleansed.  The  author  has 
seen  broad,  thick  cakes,  of  a  very  clear  pale-green  glass,  formed 
from  some  of  these  coals  in  the  furnace. 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  275 

Weight  for  weight,  coke  and  charcoal  give  out  about  equal 
heat.  But,  bulk  for  bulk,  coke,  being  denser  than  charcoal, 
possesses  a  greater  calorifying  power.  At  high  temperatures, 
this  difference  amounts  to  as  much  as  10  per  cent,  in  favor  of 
coke.  Coke,  however,  is  difficult  to  kindle,  and,  for  its  perfect 
combustion,  requires  a  strong  draught. 

From  what  has  already  been  said,  it  will  be  seen  that  fuel 
should  not  be  thrown  at  random  into  the  furnaces,  but  should  be 
carefully  selected,  so  that  the  pieces  shall  be  nearly  uniform  in 
size.  If  there  is  much  dust  in  the  coke  or  coal,  it  will,  as  we 
have  already  seen,  fill  up  the  interstices  between  the  pieces  and 
choke  the  draught.  If  the  fuel  be  too  large,  the  heating  will  go 
on  too  slowly.  Coal  or  coke,  for  ordinary  crucible  operations, 
should  be  broken  as  nearly  as  possible  into  cubes  of  an  inch  or 
an  inch  and  a  quarter  on  a  side. 

MEASUREMENT  OF  THE  HEAT  OF  FURNACES. 

Instruments  used  for  the  purpose  of  estimating  the  high 
heats  produced  by  furnaces  have  been  called  pyrometers.  Of 
these,  there  are  two  which  have  attracted  special  attention,  one 
invented  by  "VVedgewood  and  the  other  by  Daniell. 

Wedgewood's  pyrometer  consisted  of  a  gauge  and  pieces  of 
clay.  The  gauge  is  a  plate  of  brass,  with  two  rulers  of  the 
same  substance  firmly  fixed  in  it.  These  gradually  approach 
one  another  in  the  diameter  of  the  space  inclosed  by  them, 
the  entire  diminution  amounting  to  two-tenths  of  an  inch.  The 
test-pieces  are  made  of  clay,  finely  powdered,  sifted,  and  mixed 
with  water,  and  then  passed  through  an  iron  tube  and  cut  into 
cylinders  of  a  suitable  length.  When  dry,  they  are  carefully 
adapted  to  the  zero  of  the  gauge.  One  of  two  of  these  is  put 
into  the  furnace  and  heated  to  the  full  power  of  the  fire.  It  is 
then  withdrawn,  placed  between  the  rulers,  and  pushed  on  till  it 
is  stopped  by  the  narrowness  of  the  passage.  The  degree  of 
heat  is  then  calculated  from  the  contraction  it  has  undergone. 

This  process  is  objectionable  on  account  of  the  material 
selected  for  the  test-pieces.  Clay  contracts  as  powerfully  when 
subjected  for  a  long  time  to  a  low  heat  as  when  exposed  for  a 


276      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

shorter  period  to  a  higher  one.  Consequently,  the  results 
ohtained  by  Wedgewood's  instrument  are  enormous  exaggera- 
tions. Thus,  he  sets  down  the  melting-point  of  cast-iron  at 
17,977°  of  Fahrenheit,  whereas  in  fact  it  is  only  2,786°. 

Guyton  suggested  a  pyrometer  to  obviate  these  difficulties, 
and  Daniel!  constructed  a  very  finished  one,  on  the  principle  laid 
down  by  the  French  chemist. 

"It  consists  of  two  parts,  which  may  be  distinguished  as  the 
register,  1,  and  the  scale,  2,  Fig.  50.    The  register.  A,  is  a  solid 

Fip.  50. 


bar  of  black-lead  earthenware  highly  baked.  In  this  a  hole,  a  a, 
is  drilled,  into  which  a  bar  of  any  metal,  six  inches  long,  may 
be  dropped,  and  which  will  then  rest  upon  its  solid  end.  A 
cylindrical  piece  of  porcelain,  <?,  called  the  index,  is  then  placed 
upon  the  top  of  the  bar,  and  confined  in  its  place  by  a  ring  or 
strap  of  platinum,  d^  passing  round  the  top  of  the  register, 
which  is  partly  cut  away  at  the  top,  and  tightened  by  a  wedge 
of  porcelain,  e.  When  such  an  arrangement  is  exposed  to  a 
high  temperature,  it  is  obvious  that  the  expansion  of  the  metallic 
bar  will  force  the  index  forward  to  the  amount  of  the  excess  of 
its  expansion  over  that  of  the  black-lead,  and  that  when  again 
cooled  it  will  be  left  at  the  point  of  greatest  elongation.  What 
is  now  required  is  the  measurement  of  the  distance  which  the 
index  has  been  thrust  forward  from  its  first  position,  and  this. 


METHODS  OF  APPLYING  HEAT,  FURNACES,  ETC.  277 

though  in  any  case  but  small,  may  be  eflfected  with  great  precision 
by  means  of  the  scale. 

"  This  is  independent  of  the  register,  and  consists  of  two  rules 
of  brass,  //,  and  ^,  accurately  joined  together  at  a  right  angle 
by  their  edges,  and  fitting  square  upon  two  sides  of  the  black- 
lead  bar.  At  one  end  of  this  double  rule,  a  small  plate  of  brass, 
7i,  projects  at  a  right  angle,  which  may  be  brought  down  upon 
the  shoulder  of  the  register  formed  by  the  notch  cut  away  for 
the  reception  of  the  index.  A  movable  arm,  D,  is  attached  to 
this  frame,  turning  at  its  fixed  extremity  on  a  centre  ^,  and  at 
its  other  end  carrying  the  arc  of  a  circle,  whose  radius  is  exactly 
five  inches,  accurately  divided  into  degrees,  and  thirds  of  a 
degree.  Upon  this  arm,  at  the  centre  of  the  circle  k,  another 
lighter  arm,  C,  is  made  to  turn,  one  end  of  which  carries  a 
nonius,  H,  with  it,  which  moves  upon  the  face  of  the  arc,  and 
subdivides  the  former  graduation  into  minutes  of  a  degree ;  the 
other  end  crosses  the  centre,  and  terminates  in  an  obtuse  steel 
point  m,  turned  inwards  at  a  right  angle. 

"When  an  observation  is  to  be  made,  a  bar  of  platinum  or 
malleable  iron  is  placed  in  the  cavity  of  the  register;  the  index 
is  to  be  pressed  down  upon  it  and  firmly  fixed  in  its  place  by  the 
platinum  strap  and  porcelain  wedge.  The  scale  is  then  to  be 
applied  by  carefully  adjusting  the  brass  rule  to  the  sides  of  the 
register,  and  fixing  it  by  pressing  the  cross-piece  upon  the 
shoulder,  and  placing  the  movable  arm  so  that  the  steel  part  of 
the  radius  may  drop  into  a  small  cavity  made  for  its  reception, 
and  coinciding  with  the  axis  of  the  metallic  bar.  The  minute  of 
the  degree  must  then  be  noted  which  the  nonius  indicates  upon 
the  arc.  A  similar  observation  must  be  made  after  the  register 
has  been  exposed  to  the  increased  temperature  which  it  is  de- 
signed to  measure,  and  again  cooled,  and  it  will  be  found  that 
the  nonius  has  been  moved  forward  a  certain  number  of  degrees 
or  minutes.  The  scale  of  this  pyrometer  is  readily  connected 
with  that  of  the  thermometer  by  immersing  the  register  in  boil- 
ing mercury,  the  temperature  of  which  is  as  constant  as  that  of 
boiling  water,  and  has  been  accurately  determined  by  the  ther- 
mometer.    The  amount  of  expansion  for  a  known  number  of 


278   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


degrees  is  thus  determined,  and  the  value  of  all  other  expansion 
may  be  considered  as  proportionate." 

The  following  is  a  list  of  the  melting-points  of  some  of  the 
metals ;  and  it  is  obvious  that,  in  an  assay  of  each  particular 
metal,  the  temperature  employed  must  exceed  by  a  considerable 
number  of  degrees  its  melting-point.  The  table  is,  therefore, 
very  useful. 

Fahrenheit. 

-Tin  melts  at 422° 

-^Bismuth 497 

-^Lead 612 

>xZinc 773 

^Cadmium 442 

-Silver 1,860 

Copper 1,996 

-Gold 2,016 

^Cast-iron 2,786 

^Cobalt  and  nickel  rather  less  fusible  than  iron. 


(P. 


Daniell. 


CHAPTER   II 


GOLD. 


Gold  is  one  of  the  longest  known  of  all  the  metals.  Being 
usually  found  native,  and  capable  of  being  smelted  in  a  rude  way 
without  difficulty,  it  is  well  adapted  to  attract  the  attention  of 
the  savage  and  excite  his  cupidity ;  while  its  rarity,  as  well  as 
its  intrinsic  value,  gives  it  a  most  powerful  influence  over  civil- 
ized man. 

It  is  occasionally  found  crystallized  in  octahedra,  cubes,  and 
allied  forms.  These,  however,  are  not  absolutely  pure,  but 
usually  contain  silver  and  sometimes  copper,  ami  that  too  in 
no  definite  proportion,  as  will  be  seen  by  the  following  table,  the 


GOLD.  279 

first  and  second  analyses  in  which  have  been  made  by  Boussin- 
gault,  and  the  others  by  Rose  : — 


Gold. 

Silver. 

1. 

Crystal  from  Transylvania 

64.52 

35.84 

2. 

"               Marmato 

73.45 

26.48 

3. 

"               Titiribi 

76.41 

23.12 

4. 

"               Beresow 

91.88 

8.03 

5.         "  Katharinenburg       93.34  6.28 

Awdejew  found  the  silver  in  the  crystals  from  Katharinen- 
burg to  vary  from  3.86  to  28.3  per  cent.  Gold  is  more  com- 
monly found  in  spangles,  rolled  grains,  laminae,  masses  of  variable 
size,  irregular  or  arborescent,  and  in  threads  of  various  sizes 
twisted  into  a  chain  of  minute  octahedral  crystals. 

Its  geological  situations  are  the  crystalline  primitive  rocks, 
the  compact  transition  rocks,  the  trachytic  and  trap  rocks,  and 
alluvial  grounds.  It  never  is  found  constituting  a  vein  by  itself, 
like  the  baser  metals.  It  is  disseminated  through  the  rocky 
masses,  or  spread  out  on  their  surface,  or  imbedded  in  their 
cavities.  The  minerals  composing  the  veins  are  usually  either 
quartz,  calcspar,  or  sulphate  of  baryta.  The  gold  may  either 
be  directly  imbedded  in  these  minerals,  as,  for  example,  in  the 
quartz  of  California,  or  it  may  be  distributed  through  masses  of 
other  ores  contained  in  the  veins,  as  in  the  iron  pyrites  of  Vir- 
ginia, or  it  may  be  combined  with  another  metal  as  a  sort  of 
natural  alloy,  as  in  the  telluret  and  the  sulpho-plumbiferous  tel- 
luret  of  gold  of  Nagyag  in  Transylvania.  The  most  common 
ores  containing  gold  are  iron,  copper,  and  arsenical  pyrites,  ga- 
lena, and  blende  (sulphuret  of  zinc).  In  the  auriferous  pyrites 
the  gold  is  commonly  invisible  till  the  ore  is  roasted,  after  which 
the  bright  spangles  of  the  precious  metal  can  be  easily  detected 
by  the  naked  eye,  even,  it  is  said,  when  they  amount  to  no  more 
than  the  five-millionth  part  of  the  entire  weight  of  the  ore. 

In  the  primitive  rocks,  gold  occurs,  disseminated  in  small 
grains,  spangles,  and  crystals.  In  secondary  rocks  it  has  not 
been  found,  but  it  exists  in  considerable  quantity  in  trap.  Thus, 
in  Hungary,  Transylvania,  and  South  America,  trachyte  is  the 
gold-bearing  rock.     The  primary  source  of  the  metal  is  supposed 


280      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

to  be  in  the  sienite  and  greenstone  porphyry,  which  underlie  the 
igneous  rocks.  In  alluvial  grounds,  gold  is  more  commonly 
found  than  anywhere  else.  It  is  there  disseminated  in  spangles 
through  the  sands  of  certain  plains  and  rivers,  especially  in  their 
re-entering  angles,  at  low  water,  and  after  storms  and  floods.  It 
was  formerly  supposed  that  the  gold  was  washed  down  from  the 
mountains  where  the  rivers  originated,  but  good  reasons  have 
been  given  for  believing  that  it  comes  from  the  plains  through 
which  these  streams  cut  their  way.  On  the  coast  of  California, 
this  metal  is  found  in  the  sands  of  the  ocean,  at  a  little  distance 
from  the  shore.  For  miles  along  the  coast  to  the  north  of 
San  Francisco,  the  lead  used  for  soundings  brings  up  a  black 
heavy  sand,  which  contains  spangles  of  gold.  Gold  is  also  found 
in  pebbles  in  tertiary  strata.  I  have  in  my  possession  a  frag- 
ment of  beautiful  native  gold,  which  was  taken  out  of  a  quartz 
pebble  picked  up  among  a  host  of  similar  rolled  pebbles,  on  one 
of  the  gravel  hills  in  the  city  of  Baltimore.  The  metal,  as 
originally  broken  out  of  the  stone,  weighed  about  two  penny- 
weights. Other  pebbles  were  found  in  the  same  hill,  containing 
small  spangles  of  the  precious  metal. 

The  geographical  distribution  of  gold  is  very  extensive.  The 
most  important  European  mines  are  those  of  Hungary  and  Tran- 
sylvania, and  those  worked  by  Russia  in  the  Ural  mountains.  In 
Asia,  the  mines  of  this  metal  are  numerous  and  productive. 
Japan,  Formosa,  Ceylon,  Java,  Sumatra,  Borneo,  and  other 
islands  of  the  Indian  Archipelago  abound  in  the  precious  metal. 
Africa,  the  ancient  country  of  gold,  still  produces  it.  The  gold 
of  Kordofan,  the  Gold  Coast,  and  Sofala  may  be  named.  Wash- 
ings are  common  in  Virginia  and  North  Carolina,  Mexico,  and 
some  of  the  South  American  States  also  furnish  this  metal.  But 
all  other  gold  countries  in  the  world  must  yield  to  the  superior 
productiveness  of  California  and  Australia. 

METALLURGIC  TREATMENT  OF  GOLD  ORES, 

Washing. — The  metallurgic  treatment  of  gold  varies  of  course 
with  the  circumstances  under  which  it  is  obtained.  The  rudest 
method  is  what  is  known  in  Virginia  and  North   Carolina  as 


GOLD.  281 

"panning  out."  It  consists  simply  in  agitating  the  sand  in  a 
pan  with  water,  washing  off  the  lighter  particles  of  earth  till  the 
gold,  from  its  greater  specific  gravity,  is  left  nearly  pure  at  the 
bottom  of  the  pan.  Fusion  with  some  suitable  flux  completes 
the  reductionj 

In  Hungary,  this  method  is  somewhat  modified.  A  plank, 
with  twenty-four  transverse  grooves,  is  held  in  an  oblique  position. 
In  the  first  of  these  grooves  the  auriferous  sands  are  placed ; 
water  is  then  thrown  over  them  till  the  greater  part  of  the  sand 
is  washed  away.  The  gold,  mixed  with  the  minimum  of  sand, 
collects  in  the  lower  grooves,  whence  it  is  removed  into  a  flat 
wooden  basin,  and,  by  a  peculiar  sleight-of-hand,  acquired  by 
long  practice,  the  metal  is  entirely  separated.  These  operations 
remove  the  larger  spangles  of  gold ;  the  smaller  particles  are  ex- 
tracted by  amalgamation. 

—  In  our  gold  works,  the  processes  of  washing  and  amalgamation 
are  sometimes  performed  together.     The  cradle  is  one  of  the 
forms  of  apparatus  which  is  thus  applied.      This  is  a  swinging 
trough,  the  motion  of  which  resembles  that  of  the  piece  of  fur-  * 
niture  from  which  it  takes  its  name.     The  trough  is  divided  by  ; 
a  grating  into  two  compartments,  the  lower  of  which  contains  ; 
the  mercury,  and  the  upper  the  ore.     While  the  instrument  is  ' 
agitated,  a  stream  of  water  pours  over  the  ore,  and  sweeps  off  the 
lighter  sand,  while  the  gold,  with  a  portion  of  the  earthy  matter, 
drops  through  the  grating  into  the  mercurial  bath,  where  it  is 
amalgamated. 

Stamping. — This  process  is  used  to  reduce  the  coarser  sand 
ores  and  the  rocks  which  contain  gold  to  a  sufficient  fineness  to 
enable  the  workmen  to  wash  with  advantage,  or  to  use  any  other 
metallurgic  method  of  separating  the  metal.  I  High  hopes  were 
entertained  of  the  results  of  this  process*applied  to  the  gold- 
bearing  quartz  of  California,  but  these  expectations  have  been 
very  generally  disappointed.  But  one  or  two  of  the  numerous 
stamping-mills  erected  in  that  land  of  gold  have  paid  their  ex- 
penses. This  unfortunate  result  is  to  be  attributed  to  a  variety 
of  causes.  Incompetence  in  the  superintendents  of  the  mills, 
injudicious  selection  of  localities,  the  high  price  of  labor,  the 
great  irregularity  and  uncertainty  of  the  supply  of  water,  are 


282      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

some  of  the  elements  of  this  failure.  The  operations  of  stamping 
and  washing  are  often  performed  at  the  same  time,  a  stream  of 
water  sweeping  over  the  ore  while  it  is  being  pulverized,  and 
carrying  it  over  hides  or  blankets.  Upon  the  rough  surfaces  of 
these  the  gold,  mixed  with  some  sand,  is  deposited. 

The  auriferous  sulphurets  of  the  baser  metals  must  be  ma- 
naged in  a  different  manner.  When  properly  treated,  they  yield 
a  good  interest  on  the  money  and  labor  invested,  though,  as  a 
general  thing,  they  are  much  poorer  than  the  last-named  ores. 
Some  contain  only  one  two-hundred-thousandth  part  of  gold, 
and  yet  have  been  worked  to  advantage.  They  are  first  roasted 
in  the  open  air,  or  in  a  calciner  with  a  draught  over  its  bed,  in 
order  to  drive  off  sulphur,  and  peroxidize  the  metals.  In  some 
establishments,  the  oxidation  is  effected  at  the  common  tempera- 
ture of  the  atmosphere,  the  action  of  the  oxygen  being  facili- 
tated by  the  admixture  of  common  salt  with  the  finely  commi- 
nuted ore.  After  this,  some  rely  on  washing  (an  imperfect  pro- 
cess), to  separate  the  gold. 

Fusion. — Rich  ores  of  gold,  in  which  there  is  no  alkaline  sul- 
phuret  to  dissolve  the  sulphuret  of  the  metal,  may  be  directly 
fused  with  any  thin  flux,  that  will  sufficiently  act  upon  the  stony 
matters  of  the  gangue. 

Fusion  is  used  with  two  objects  ;  the  one  is  to  separate  the 
metals  from  adhering  stone,  the  other  to  smelt  out  a  metallic 
mass  which  can  be  directly  cupelled.  The  rich  mattes  (metallic 
oxides  and  sulphurets  containing  metal)  obtained  by  the  first  fu- 
sion, are  again  roasted  to  complete  the  oxidation  of  the  baser 
metals.  The  calcined  mass  is  then  fused  with  lead,  which  combines 
with  the  gold,  and  is  separated  from  it  by  cupellation.  Gold 
ore,  containing  mi|ch  copper,  is  better  treated  by  amalgamation. 

Cupellation. — The  rationale  of  this  process  is  very  simple.  It 
depends  upon  the  tendency  of  some  metallic  oxides  to  run  through 
a  porous  substance  which  remains  impermeable  to  the  purer  un- 
oxidated  metals.  It  is  a  cheap,  rapid,  and,  if  properly  con- 
ducted, certain  method  of  purifying  the  noble  metals.  It  will 
be  treated  of  under  the  head  of  the  Metallurgy  of  Alloys  of 
Silver. 
f  Amalgamation. — Mercury  has  a  powerful  affinity  for  most 


GOLD.  283 

metals,  forming  an  amalgam,  when  fairly  brought  in  contact 
with  them.  This  property  of  mercury  is  taken  advantage  of  by 
those  who  work  in  the  precious  metalsX  Formerly  much  mer- 
cury was  lost  in  consequence  of  the  careKss  manner  in  which  it 
was  used.  At  present,  however,  the  prVcess  is  better  under- 
stood, and  its  results  are  more  favorable.  IThe  mode  commonly 
employed  is  that  of  revolving  barrels.  The  ore  is  introduced 
into  the  barrels,  and  they  are  made  to  revolve  rapidly  till  the 
gold  is  all  taken  up.  The  liquid  amalgam  is  then  allowed  to 
settle  down  in  the  barrels,  when  it  is  drawn  off,  and  pressed  in 
bags  of  strong  fine  canvas,  of  chamois  leather,  or  of  buckskin. 
In  this  manner  the  excess  of  mercury  is  forced  out  through  the 
pores  of  the  bag,  and  there  is  left  behind  a  pasty  amalgam. 
This  is  decomposed  by  distillation  in  cast-iron  retorts,  by  means 
of  which  the  mercury  is  drawn  over,  and  the  gold  remains  in 
the  retort  in  a  spongy  state.  The  gold  thus  obtained  is  usually 
free  from  all  foreign  metals  except  silver.  This  is  easily  sepa- 
rated from  the  alloy  by  the  operation  of  parting.^ 

In  the  Southern  States  of  our  Union,  some  difficulty  is  expe- 
rienced in  managing  amalgamation  with  economy.  The  deeper 
ores  are  all  decidedly  pyritous,  and,  independently  of  the  loss 
of  mercury  by  its  combination  with  sulphur,  the  particles  of  gold 
are  so  protected  and  shielded  from  the  action  of  the  liquid 
metal  that  but  a  fraction  of  what  the  ore  actually  contains  is 
extracted.  Gold  ore,  for  example,  containing  from  thirty  to 
seventy  dollars'  worth  of  metal  to  the  ton,  is  crushed,  oxidated, 
and  amalgamated.  Only  a  portion  of  the  gold  is  thus  obtained. 
The  residual  ore  is  then  exposed  again  to  the  action  of  the 
atmosphere  for  a  year,  and  so  more  deeply  oxidated.  It  is  then 
again  amalgamated,  and  I  have  been  assured  by  gold  miners  in 
Virginia,  that  they  have  obtained  more  gold  from  the  second 
than  from  the  first  amalgamation.  These  operations  are  some- 
times repeated  four  or  five  times,  more  or  less  metal  being  ob- 
tained at  every  repetition.  This  is  very  expensive,  and  the 
poorer  varieties  of  ore  will  not  pay  for  roasting  by  the  fire. 

It  is  hardly  necessary  to  add  that  the  quicksilver  must  be 
used  in  considerable  excess,  for,  should  it  become  pasty,  it  will 


284      CHEMISTRY  OP  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

not  absorb  the  gold,  and  will,  besides,  be  difficult  to  separate 
from  the  pounded  ore  with  which  it  is  mixed. 

METALLURGY  OF  THE  ALLOYS  OF  GOLD. 

The  purification  of  alloys  of  gold,  or  rather  the  separation  of 
other  metals  from  gfld,  is  effected  either  in  the  wet  or  the  dry 
way.  The  latter  is  the  mode  most  frequently  adopted  for  the 
separation  of  the  more  common  metals. 

The  fragments  of  gold  swept  up  in  the  goldsmith's  shop,  or 
in  the  mechanical  room  of  a  dentist,  are  mixed  with  many  other 
metals,  and  with  earthy  and  other  impurities.  The  latter  are 
got  rid  of,  in  part,  by  washing ;  the  former  separated  by  fusion 
with  oxidating  reagents.  These  are  numerous,  but  the  most 
energetic  of  them  are  litharge  and  nitre. 

The  nitrates  of  potash  and  soda  are  easily  decomposable  at  a 
full  red  heat.  They  lose  oxygen,  and  are  converted  into  nitrites. 
The  oxygen^ontained  by  these  salts  being  in  large  proportion 
and  easily  sepai'able,  they  readily  communicate  it  to  the  oxidable 
metals  fused  with  them.  The  oxides  formed  in  this  manner 
enter  into  fusion,  and,  being  lighter  than  the  metals  to  be  re- 
fined, float  on  the  surface  of  the  metallic  bath  in  a  slag,  of  a 
fluidity  and  brightness  corresponding  to  the  amount  of  the  flux. 
Schlutter  used,  for  this  poor  refuse,  mixtures  of  glass  with  car- 
bonate of  potassa,  litharge,  and  granulated  lead.  Borax  con- 
stitutes another  valuable  addition  to  these  oxidating  reagents, 
because,  while  it  possesses  considerable  oxidating  powers,  it  has 
also  the  advantage  of  being  an  universal  flux,  and  is,  conse- 
quently, particularly  applicable  to  refining  processes  in  which 
the  operator  is  compelled  to  contend  with  earthy  impurities. 

Scorification, — This  is  a  process  which  furnishes  an  alloy  well 
adapted  for  cupellation,  while  it  oxidates  the  baser  metals.  It 
will  be  described  under  the  head  of  Alloys  of  Silver.  We  will 
only  say  that,  when  this  process  is  adopted,  it  must  be  pushed 
to  the  thorough  removal  of  all  tin  and  zinc,  because  the  cupel- 
lation would  otherwise  be  ruined,  the  gold  being  projected  by 
the  violence  of  the  ebullition. 

Tin  is  a  particularly  troublesome  component  of  a  gold  alloy. 


GOLD.  285 

as  the  smallest  quantity  of  it  communicates  the  most  intractable 
character  to  this  metal.  It  gives  it  a  remarkable  hardness  and 
brittleness.  The  mere  exposure  of  a  bar  of  gold  to  the  vapors 
arising  from  a  bath  of  redhot  tin,  is  sufficient  to  destroy  its  mal- 
leability and  make  it  brittle.  This  impurity  is  easily  got  rid  of 
by  fusion  with  corrosive  sublimate  or  with  nitre.  The  first  of 
these  agents  converts  the  metal  into  the  volatile  perchloride  of 
tin,  which  passes  off  with  the  mercury  in  vapor,  leaving  the 
metallic  bath  entirely  free  from  tin.  The  second  removes  it  by 
oxidating  it  to  stannic  acid,  so  that  it  is  all  contained  in  the 
slag,  which  consists  chiefly  of  stannate  of  potash. 

Sulpliuret  of  Antimony. — Sulphuret  of  antimony,  or  crude 
antimony,  as  it  is  called  in  commerce,  is  one  of  our  most  power- 
ful means  of  separating  gold  from  its  alloys.  Iron,  tin,  zinc, 
and  even  silver  are  got  rid  of  by  means  of  this  reagent,  which 
is  a  favorite  one  with  goldsmiths  who  wish  to  bring  their  gold  to 
a  very  high  standard.  The  alloy  is  heated  in  a  crucible,  and, 
when  in  a  state  of  perfect  fusion,  from  twice  to  four  times  its 
weight  of  very  pure  sulphuret  of  antimony  is  carefully  thrown 
upon  it.  To  this  some  add  sulphur,  when  the  quantity  of  silver 
in  the  alloy  exceeds  one-third.  It  must  be  heated  moderately, 
to  avoid  spirting,  and  the  melting  substance  must  be  sedulously 
guarded  against  the  accidental  intrusion  of  cinders  from  the 
fire.  Should  a  fragment  of  coal  fall  in,  a  violent  effervescence 
will  take  place,  which  will  throw  the  contents  of  the  crucible 
over  its  sides  and  cause  great  loss.  The  crucible,  to  avoid  loss, 
should  be  so  large  that  the  alloy  and  the  crude  antimony  will 
not  occupy  more  than  two-thirds  of  its  cavity.  The  foreign 
metals  all  unite  with  the  sulphur,  and  the  gold,  alloyed  with  the 
antimony,  sinks  to  the  bottom.  When  the  fusion  has  become 
perfectly  tranquil,  the  mixture  is  poured  into  a  conical  ingot- 
mould  of  iron,  in  which  the  same  stratification  of  the  alloys  and 
the  sulphurets  takes  place.  The  fusion  is  repeated  with  fresh 
quantities  of  sulphuret  of  antimony  as  often  as  may  be  judged 
necessary. 

The  antimony  must  now  be  separated  from  the  alloy.  For 
this  purpose  it  may  be  roasted  in  a  muffle,  and  then  smelted 
with  borax,  nitre,  and  glass ;  two  parts  of  the  first  to  one  of 


286      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

each  of  the  others.  Bj  this  process,  however,  gold  is  lost.  A 
more  efficient  roasting  is  accomplished  in  the  following  manner : 
The  gold  is  fused  in  a  crucible,  and,  when  well  heated,  the  blast 
from  a  pair  of  bellows  is  thrown  upon  it.  At  first  it  is  neces- 
sary to  be  very  cautious,  as  too  great  a  draught  hurries  the  vola- 
tilization of  the  antimony,  so  that  some  gold  is  carried  off  with 
it.  The  current  of  air  should  be  just  strong  enough  to  produce 
visible  fumes.  When  the  gold  is  nearly  pure,  it  seems  to  thicken 
and  is  covered  with  a  film.  The  heat  is  then  increased  and  the 
crucible  closed  for  a  short  time.  The  cover  is  now  taken  off, 
and  a  current  of  air  again  driven  over  the  surface  of  the  metal 
for  a  few  minutes.  Lastly,  the  fire  is  strongly  urged,  to  drive 
off  any  remaining  particles  of  antimony. 

The  alloy  of  gold  and  antimony  may  be  fused  with  nitre. 
When  this  method  is  adopted,  the  alloy,  with  three  times  its 
weight  of  the  salt,  is  placed  in  a  crucible,  covered  with  another 
reversed,  and  pierced  in  the  bottom  with  a  hole,  which  may  be 
stopped  with  a  plug  of  clay.  It  is  to  be  gradually  heated  from 
above  downwards,  to  avoid  bubbling  over.  This  is  easily  accom- 
plished by  leaving  the  furnace  uncovered,  using  a  charcoal  fire, 
and  kindling  it  from  above.  So  long  as  any  undecomposed 
nitre  remains,  a  lighted  coal,  applied  to  the  hole  in  the  covering 
crucible,  burns  with  great  brilliancy,  in  consequence  of  the 
oxygen  ascending  from  the  decomposing  salt.  As  soon  as  this 
evolution  of  gas  ceases,  the  heat  may  be  pushed  without  fear  of 
spirting. 

Galena,  or  sulphuret  of  lead  may  be  substituted  for  antimony 
in  the  above-described  operation.  In  this  case,  however,  the 
metallic  button  contains  silver  as  well  as  gold.  The  two  metals 
in  combination  can  be  separated  from  the  lead  by  cupellation. 

Sulphur. — All  these  methods  are  based  upon  the  greater  affin- 
ity of  sulphur  for  other  metals  than  for  gold.  This  metalloid 
can,  therefore,  be  used  alone,  and  is  sometimes  employed  for  this 
purpose.  Gold  is  occasionally  refined  by  melting  it  in  a  clay 
crucible,  and,  when  in  full  fusion,  throwing  into  it  a  few  bits  of 
sulphur  as  large  as  a  pea.  The  crucible  is  well  shaken  and  its 
contents  poured  into  an  ingot-mould. 

Peroxide  of  manganese  has  been  used  to  separate  gold  and 


GOLD.  287 

silver  from  the  common  metals.  The  alloy  is  either  reduced  to 
powder  or  finely  laminated  in  a  flatting-mill,  and  then  fused 
with  peroxide  of  manganese  and  bottle-glass.  The  foreign 
metals  are  oxidated  and  float  up  in  the  slag.  The  silver  is  found 
usually  combined  with  the  gold,  though  a  portion  of  it  is  oxidized 
and  diffused  through  the  slag. 

Many  of  the  alloys  of  gold  can  be  directly  cupelled.  That 
with  lead  is  usually  subjected  to  this  operation.  It  is  less  dif- 
ficult than  the  cupellation  of  silver,  as  gold  does  not  have  the 
same  tendency  to  penetrate  the  cupel,  nor  does  it  volatilize  nor 
vegetate  like  that  metal.  A  higher  heat  can  therefore  be  used 
without  fear  of  loss,  and  indeed  it  improves  the  quality  of  the 
gold. 

An  alloy  of  gold  and  copper  cannot  be  cupelled,  in  the  large 
way,  to  any  advantage,  on  account  of  the  great  quantity  of  lead 
necessary  to  carry  off"  the  copper,  and  the  consequent  consump- 
tion of  time  and  fuel.  According  to  Mitchell,  fourteen  parts  of 
lead  at  least  must  be  used  in  the  alloy  of  gold  coin,  which  con- 
tains 0.100  of  copper.  Besides,  gold  has  so  strong  an  affinity 
for  copper,  that,  although  the  utmost  caution  has  been  observed, 
it  still  retains  a  portion  of  this  metal  after  cupellation.  The 
humid  process  is  less  objectionable. 

The  presence  of  platinum  in  an  alloy  greatly  increases  the 
difficulty  of  cupellation.  This  process  cannot,  indeed,  be  accom- 
plished without  the  addition  of  silver,  if  that  metal  be  not  already 
present.  The  separation  of  the  copper  is  effected  with  less 
waste  of  silver,  by  using  a  small  quantity  of  lead  and  cupelling 
at  a  high  temperature,  than  by  employing  more  lead  and  a  lower 
heat.  The  presence  of  platinum  in  an  alloy  of  gold  may  be 
distinguished,  according  to  Mitchell,  by  the  following  characters, 
independent  of  actual  analysis  :  "  If  the  assay  be  not  heated 
very  strongly,  it  does  not  pass,  and  the  button  becomes  flat ; 
this  eff'ect  becomes  very  sensible,  when  the  platinum  is  to  the 
gold,  in  the  proportion  of  2  to  100.  Under  the  same  circum- 
stances, the  nitric  acid  solution  proceeding  from  the  parting,  is 
colored  straw  yellow.  At  the  moment  an  assay  of  an  alloy 
containing  platinum  terminates,  the  motion  is  slower,  and  the 
colored  bands  are  less  numerous,  more  obscure,  and  remain  a 


288      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

much  longer  time  than  when  there  is  no  platinum ;  the  button 
does  not  uncover,  and  the  surface  does  not  become  as  brilliant 
as  that  of  an  alloy  of  gold  or  silver,  but  it  remains  dull  and 
tarnished.  When  the  assay  is  well  made,  it  is  to  be  remarked 
that  the  edges  of  the  button  are  thicker  and  more  rounded  than 
in  ordinary  assays,  and  it  is  of  a  dull  white,  approaching  a  little 
to  the  yellow ;  and,  lastly,  its  surface  is  wholly,  or  in  part, 
crystalline.  These  effects  are  sensible,  even  when  the  gold  does 
not  contain  more  than  0.01  of  platinnm.  When  the  alloy  con- 
tains more  than  ten  parts  of  platinum  to  90  of  gold,  the  an- 
nealed cornet  produced  in  the  parting  process,  is  of  a  pale  yellow 
or  tarnished  silver  color."* 

Parting. — This  is  a  term  applied  exclusively  to  the  separation 
of  gold  from  silver.  There  are  two  kinds,  the  wet  and  the  dry 
parting. 

ry  Parting. — This  method  is  employed  in  the  treatment  of 
very  poor  alloys  of  gold,  to  concentrate  it  to  a  less  proportion 
of  silver,  and  to  give  a  surface  refining  to  certain  alloys  of  gold 
and  copper.  The  concentrated  parting,  as  it  was  called,  con- 
sisted in  stratifying  the  laminated  alloy  with  a  cement  varying 
in  its  composition.  Some  employed  equal  parts  of  sulphate  of 
iron  and  common  salt ;  others,  2  parts  of  sulphate  of  iron,  2 
parts  of  sea  salt,  and  1  of  chloride  of  ammonium,  &c.  Burnt 
clay  or  finely  powdered  brick,  to  the  amount  of  three  or  four 
times  the  weight  of  the  mixture,  is  added,  and  the  whole  made 
into  a  thick  paste.  The  mixture  is  heated  gradually  to  dull 
redness,  and  kept  at  that  temperature  for  twenty-four  hours,  the 
alloy  not  being  permitted  to  fuse.  The  rationale  of  this  process 
is  very  simple.  Sulphate  of  iron  parts  with  its  acid  at  a  dull 
red  heat  The  sulphuric  acid,  arising  from  this  decomposition, 
attacks  the  base  of  the  chloride,  and  the  disengaged  chlorine 
combines  with  the  silver.  The  same  mixture  is  sometimes  used, 
with  this  difference,  that  nitre  is  substituted  for  salt  and  sal 
ammoniac.  In  this  case,  the  liberated  sulphuric  acid  unites  with 
the  potash  of  the  nitre,  setting  free  nitric  acid,  which  acts  to 
great  advantage  at  this  temperature,  refining  alloys  which  it 
would  not  touch  in  the  wet  way.    Frequent  fusions,  laminations, 

*  Manual  of  Assaying. 


GOLD.  289 

and  cementations  are  necessary  in  order  to  attain  anything  like 
purity. 

The  parting  by  sulphur  is  applicable  to  alloys  containing  a 
very  small  amount  of  gold,  as  small  a  quantity  as  jooii  of  gold 
being  extracted  from  silver  without  loss. 

To  accomplish  parting  by  this  method,  the  alloy  is  first  fused 
and  granulated  by  being  dropped  into  Avater,  which  is  agitated 
by  a  rotary  movement  with  a  broom.  This  is  mixed  with  sulphur, 
put  into  a  crucible,  and  heated  below  the  point  of  fusion  to  form 
sulphuret  of  silver  by  cementation.  It  is  then  heated  to  com- 
plete fusion,  and  poured  into  a  conical  iron  mould,  greased  and 
heated.  Should  the  mass  be  homogeneous,  sulphuration  is  com- 
plete. It  is  then  refused,  with  addition  of  more  of  the  granu- 
lated alloy,  or  with  a  small  quantity  of  iron  filings.  Sometimes 
the  first  fusion  yields  a  button  of  suitable  richness,  and  then  the 
operation  is  complete.  Should  the  button  be  very  rich,  gold 
remains  in  the  sulphurated  mass,  and  this  must  be  fused  as 
before  with  iron.  Should  the  button  contain  excess  of  silver, 
it  must  be  fused  again  with  sulphur.  The  alloy  is  then  to  be 
roasted  and  cupelled  with  lead,  and  the  mass  of  the  sulphurets 
to  be  fused  with  iron  to  reduce  the  silver. 

A  modification  of  this  process  has  been  adopted,  viz :  to  add 
litharge  to  the  fused  mass  at  the  beginning  of  the  operation.  A 
button  then  subsides,  containing  the  greater  portion  of  the  gold 
alloyed  with  silver.  The  rest  of  the  gold  is  mixed  with  the 
sulphuretted  slag.  This  is  fused  with  litharge  till  all  the  gold 
is  extracted  from  it.    The  buttons  are  fused  again  with  sulphur. 

Wet  Parting. — This  process  may  be  conducted  with  nitric 
acid,  sulphuric  acid,  or  aqua  regia. 

A.  Nitric  Acid. — The  best  proportion  of  silver  to  gold,  in  an 
alloy  which  is  to  be  acted  upon  by  this  acid,  is  two  and  a  half 
of  the  former  to  one  of  the  latter.  Should  the  proportion  of 
silver  be  less  than  this,  it  cannot  be  thoroughly  dissolved  out, 
because  the  gold  envelops  it  in  part,  and  protects  it  from  the 
action  of  the  solvent.*     Should  the  silver  greatly  exceed  three- 

*  Pettenkofer  asserts  that  not  more  than  If  of  silver  to  1  of  gold  is 
necessary  for  the  success  of  this  process. 

19 


290  CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

fourths  of  the  alloy,  the  gold  is  obtained  in  such  fine  leaves  and 
impalpable  powder  that  some  of  it  is  infallibly  lost  in  decanta- 
tion,  and  even  in  the  operation  of  boiling  the  acid  liquid.  It  is 
necessary,  therefore,  to  bring  the  alloy  to  the  standard  of  some- 
what less  than  three  parts  of  silver  to  one  of  gold.  Three  parts 
of  the  former  to  one  of  the  latter  was  the  old  formula,  and,  in 
consequence  of  this  proportion,  the  operation  necessary  to 
accomplish  this  has  been  called  quartation,  an  appellation  some- 
times erroneously  applied  to  the  whole  process  of  nitric  acid 
parting. 

To  perform  this  correctly,  the  mixed  metals  must  be  fused, 
and  then  poured  into  a  cold  ingot-mould,  so  as  to  mix  them 
equally.  A  portion  of  the  resulting  alloy  must  be  submitted  to 
analysis,  that  we  may  ascertain  the  exact  quantities  of  silver 
and  gold  present.  This  being  determined,  the  alloy  must  again 
be  melted  with  an  additional  quantity  of  one  or  the  other  metals, 
sufficient  to  bring  it  to  the  standard  fineness.  When  the  amount 
of  alloy  operated  upon  is  not  very  large,  it  will  be  convenient 
to  do  this  upon  a  cupel,  with  the  addition  of  two  parts  of  lead. 
This  process  can  also  be  used  on  the  large  scale,  though  simple 
fusion,  if  the  alloy  is  tolerably  free  from  other  metals,  or  fusion 
with  pure  nitre,  if  it  is  much  contaminated,  is  commonly  pre- 
ferred. 

The  quartated  alloy  is  now  to  be  either  granulated,  by  pouring 
it  from  the  crucible  into  cold  water,  or,  what  is  still  better,  if 
the  quantity  be  small,  flattened  on  an  anvil,  annealed,  laminated 
in  a  mill,  annealed  again,  rolled  out  to  a  very  thin  foil,  and  then 
made  into  a  cornet  or  spiral,  by  winding  it  around  a  small 
cylinder.  The  cornet  is  now  to  be  introduced  into  a  suitable 
vessel,  pure  nitric  acid  is  to  be  poured  upon  it,  from  time  to  time, 
and  heat  applied.  When  the  silver  is  all  dissolved,  it  is  poured 
off,  and  the  gold  carefully  washed  by  decantation.  The  washing 
is  complete,  when  the  water  which  comes  off  no  longer  commu- 
nicates a  cloudiness  to  a  solution  of  common  salt,  after  standing 
several  hours. 

The  nitric  acid  must  be  poured  on  at  different  times,  and  of 
different  degrees  of  strength.  If  concentrated  acid  be  used 
from  the  beginning,  the  action  will  be  so  violent  that  some  of 


GOLD.  291 

the  gold  will  be  lost  by  spirting.  If  weak  acid  be  used  through- 
out, all  the  silver  will  not  be  dissolved.  The  old  method  of 
treating  the  cornet  was  to  pour  thirty-five  times  the  weight  of 
the  alloy,  of  nitric  acid,  at  20°  (sp.  gr.  1.15),  and  boil  gently 
for  fifteen  to  twenty  minutes ;  then  to  decant  the  liquid,  and 
replace  it  by  twenty-four  parts  of  acid  (sp.  gr.  1.26),  boil 
for  twelve  minutes,  decant  and  wash.  Vauquelin,  in  his  Manuel 
de  V Essayeur^  recommends  a  somewhat  difi'erent  process.  He 
boils  on  the  cornet  72  parts  of  acid,  at  22°  Baume  (sp.  gr. 
1.16),  for  twenty-two  minutes ;  he  then  decants  and  replaces  it 
by  from  60  to  100  parts  of  acid  at  32°  (sp.  gr.  1.26),  and  boils 
for  eight  or  ten  minutes. 

"When  a  considerable  quantity  of  copper  remains  in  the  alloy 
after  fusion  with  nitre,  or  cupellation,  this  process  is  accurate. 
When,  however,  the  alloy  is  finer,  the  gold  always  retains  a  little 
silver,  so  that  a  test  alloy  made  of  pure  gold  and  silver,  always 
yields  a  piece  of  gold,  as  separated  by  nitric  acid,  heavier  than 
that  originally  introduced.  This  excess  of  silver  is  termed  the 
surcharge^  and  usually  amounts  to  two  or  three  thousandths, 
though  it  sometimes  exceeds  this  amount.  M.  Chaudet  has 
suggested  the  following  process,  to  get  rid  of  it  entirely.  He 
cupels  the  gold,  as  already  recommended,  with  three  parts  of 
silver  and  two  of  lead ;  makes  a  cornet ;  boils  it  with  acid  of 
22°  B.,  for  three  or  four  minutes;  replaces  this  with  acid  of 
32°  B.,  and  boils  for  ten  minutes;  decants  again,  and  boils  with 
fresh  acid  of  32°  B.  for  eight  or  ten  minutes  longer.  This 
leaves  very  pure  gold. 

The  processes  of  liquid  parting  just  described  are  mainly 
those  of  the  assayer,  who  operates  on  small  quantities  of  the 
precious  metals.  They  are,  however,  applicable  to  larger 
operations  by  some  slight  modifications,  and  can  be  directly 
used  by  the  refiner  when  working  with  small  quantities  of  alloy. 

When  greater  weights  of  these  metals  are  to  be  purified,  it  is 
of  importance  to  use  such  forms  of  apparatus  as  will  avoid  loss 
of  the  materials  used  in  the  parting,  Avhich  on  the  large  scale 
become  very  valuable  of  themselves.  We  give  here  a  figure  of 
an  apparatus  which  may  be  used  for  obtaining  the  nitric  acid 
originally,  and  for  saving  it  after  parting. 


292  CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

It  consists  of  a  platinum  alembic  or  retort  {a),  mtli  a  capital 
(6),  connected  by  a  stoneware  pipe  (e),  with  a  stoneware  receiver 
(/),  which  is  set  in  a  refrigerating  tub  (g).  The  retort  has  a 
tubulure  (c),  furnished  with  a  lid  ground  air-tight,  which  may 

Fijr.  51. 


be  kept  in  place  by  a  weight.     Through  this,  acid  is  introduced, 
and  the  process  from  time  to  time  inspected.     With  the  capital 
is  connected  a  tube  of  platinum,  which,  at  its  other  end,  is  united 
with  the  stoneware  pipe  (e).     The  receiver  is  furnished  with  an 
opening  {I  /),  for  inspecting  the  condensation  of  the  acid,  and  a 
tubulure  which  receives  the  jointed  pipe  (i  2),  each  joint  entering 
conically  into  the  one  below.     The  upper  joinings  are  not  to  be 
tightly  luted,  as  the  access  of  a  little  atmospheric  air  is  desirable 
to  oxidate  the  nitrous  acid.    Water  is  to  be  supplied  in  a  gradual 
manner,  and  with  a  broad  surface,  by  filling  the  upright  pipes 
with  quartz  pebbles,  so  as  partially  to  obstruct  the  tubes,  and 
allowing  a  small  stream  of  water  to  trickle  over  them  so  slowly 
as  merely  to  keep  them  moist.     The  receiver  is  also  furnished 
with  a  glass  or  stoneware  stopcock  (h)  for  drawing  off  the  acid. 
A  small  air-furnace  {k),  furnished  with  an  iron  ring,  on  which 
the  iron  rim  of  the  platinum  retort  rests,  completes  the  appa- 
ratus.   The  refrigerating  tub  should  be  supplied  with  a  constant 
stream  of  cold  water  from  a  lead  pipe  dipping  nearly  to  its 
bottom,  the  hot  water  being  allowed  to  escape  over  the  edge  of 
the  tub. 


GOLD.  293 

The  size  of  this  apparatus  will  vary  according  to  the  purposes 
for  which  it  is  required.  That  described  by  Dr.  Ure,  from 
whose  Dictionary  the  wood-cut  has  been  copied  with  slight 
alterations,  is  estimated  to  part  100  pounds  of  alloy.  Its  capa- 
city is  ten  gallons.  The  stoneware  conducting-pipe  (e)  is  at 
least  40  feet  long,  and  the  platinum  tube,  connecting  it  with  the 
alembic,  2  feet  long.  The  tubes  (i  i)  and  {I  I)  are  3  inches  in 
diameter  and  12  feet  high.  These  dimensions  are  of  course  too 
costly  for  ordinary  operations.  The  apparatus  may  be  obtained 
at  a  very  moderate  cost,  and  in  a  much  more  compact  form,  by 
using  a  platinized  retort,  instead  of  one  made  of  pure  platina, 
and  by  making  the  connection  with  a  Liebig's  condenser,  instead 
of  the  unwieldy  stoneware  pipe. 

When  the  apparatus  is  used  for  making  nitric  acid,  100  parts 
of  pure  nitre  or  nitrate  of  soda  (which  is  better  on  account  of 
the  greater  facility  of  separating  the  resulting  sulphate  of  soda 
from  the  retort  and  its  higher  value)  is  introduced  into  the 
alembic,  the  capital  adapted,  and  the  platinum  tube  luted  to  it. 
Through  the  tubulure  c,  20  parts  of  strong  sulphuric  acid  are 
poured,  and  the  lid  of  the  tubulure  is  closed.  In  an  hour,  10 
parts  more  of  acid  are  poured  in,  and  so  in  every  hour  till  60 
parts  are  added.  A  few  hours  after  the  last  addition  of  acid, 
and  not  till  then,  a  little  fire  is  made  under  the  alembic.  In  24 
hours,  if  the  heat  has  been  properly  managed,  all  the  acid  may 
be  drawn  off.  Its  final  expulsion  is  aided  by  the  introduction  of 
boiling  water  in  successive  portions,  the  lid  of  the  tubulure  being 
closed  after  every  aspersion. 

The  best  strength  of  acid  for  parting  is  stated  by  Dr.  Ure  to 
be  that  of  specific  gravity  1.320.  A  measure,  therefore,  which 
will  hold  16  ounces  by  weight  of  distilled  water,  will  contain 
21|-  ounces  of  this  acid.  It  should  be  free  from  hydrochloric 
acid,  and  should  not  therefore  be  clouded  by  a  few  drops  of  a 
solution  of  nitrate  of  silver  in  distilled  water  after  several  hours' 
standing.  Should  any  milkiness  be  produced  by  this  reagent, 
the  acid  can  be  readily  purified,  by  dropping  into  it  a  little  silver 
in  a  state  of  minute  division,  before  it  is  used  for  the  operation 
of  parting.  Should  this  precaution  be  neglected,  there  Avill  be 
an  inevitable  loss  of  gold,  in  direct  proportion  to  the  amount  of 


294  CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

hydrochloric  acid  present,  because  that  metal  is  soluble  in  a 
mixture  of  hydrochloric  and  nitric  acids. 

In  making  a  chemical  estimate  of  the  necessary  amount  of 
acid,  we  find  that  it  requires  38  parts  of  aquafortis^  of  specific 
gravity  1.320,  to  oxidate  100  parts  of  silver,  and  111  more  to 
dissolve  it.  But  in  actual  working,  we  are  compelled  to  use 
more  of  any  given  substance  than  a  calculation  based  on  its 
combining  numbers  would  indicate,  because  towards  the  end  of 
an  operation  the  reactions,  in  consequence  of  the  gradual  satura- 
tion, become  so  feeble  that  too  much  time  is  taken  up.  Copper, 
it  must  also  be  borne  in  mind,  consumes  much  more  acid,  both 
for  oxidation  and  solution,  so  that  it  is  advisable  to  supply  silver 
freed  from  copper  by  ^  previous  operation,  and,  if  possible, 
containing  a  little  gold. 

The  alloy,  properly  prepared,  is  then  introduced  into  the 
alembic,  the  capital,  and  the  joinings  of  the  apparatus  are  made 
fast,  and  the  upright  tubes  arranged  as  for  the  manufacture  of 
nitric  acid.  For  60  parts  of  alloy  80  parts  of  acid  are  necessary. 
Ure  prescribes  for  the  composition  of  the  alloy,  two  of  silver 
to  one  of  gold,  though  there  certainly  will  be  more  gold  in  the 
surcharge,  with  an  alloy  of  this  proportion,  than  in  such  a  one 
as  has  already  been  prescribed.  The  fire  must  be  managed 
with  caution,  being  moderate  at  first,  and  gradually  increased 
as  the  parting  advances.  The  excess  of  acid  passes  over  and 
is  condensed,  and  the  nitrous  acid  fumes,  arising  from  the  de- 
composition of  the  aquafortis,  are  reconverted  into  nitric  acid 
by  the  joint  action  of  the  atmospheric  air  and  water  contained 
in  the  condensing  apparatus.  In  this  manner,  20  or  30  parts 
of  acid  may  be  saved  in  a  state  of  sufficient  purity  to  be  em- 
ployed in  a  subsequent  operation. 

When  the  action  of  the  acid  on  the  alloy  has  ceased,  which 
may  be  known  by  the  cessation  of  the  red  fumes  on  opening  the 
tubulure,  the  fire  is  extinguished,  the  alembic  cooled  and  re- 
moved. Its  liquid  contents  are  then  decanted  into  pure  water, 
and  the  gold  remaining  in  the  retort  boiled  with  some  fresh 
nitric  acid,  to  remove,  as  far  as  possible,  the  remaining  silver. 
The  heavy  gold  powder  is  now  thoroughly  washed  with  distilled 
or  rain  water,  fused  with  nitre  or  borax,  and  cast  into  ingots. 


GOLD.  295 

The  solution  of  nitrate  of  silver  is  now  precipitated  by  clean 
plates  of  copper  suspended  in  it,  the  completion  of  the  operation 
being  known  by  the  absence  of  cloudiness  on  adding  common 
salt  or  hydrochloric  acid  to  a  portion  of  the  solution.  The  pasty 
precipitate  of  metallic  silver  is  now  to  be  thoroughly  washed 
with  soft  water,  dried  by  strong  hydraulic  pressure,  fused,  and 
cast  into  ingots. 

The  blue  liquid,  which  is  a  solution  of  nitrate  of  copper,  is 
now  to  be  evaporated  to  dryness  in  the  alembic,  the  tubulure  c 
remaining  open.  When  all  the  water  is  driven  off,  the  lid  is 
put  on,  the  heat  gradually  raised,  the  apparatus  remaining  in 
the  condition  first  described,  and  the  nitric  acid  all  distilled  off, 
leaving  black  oxide  of  copper  in  the  retort.  This  is  a  useful 
substance  in  the  laboratory,  and  may  be  heated  to  redness,  and 
put  away  in  bottles  with  closely-fitting  stopples.  Or  it  may  be 
used,  if  in  large  quantity,  as  an  economical  form  for  obtaining 
the  sulphate  of  copper,  100  parts  of  it  yielding  312|  of  that 
salt  in  crystals. 

The  objections  to  this  process  have  been  already  stated.  The 
gold  obtained  by  it  always  contains  a  little  silver,  and  the  silver 
retains  a  little  gold.  Many  refiners,  therefore,  adopt  another 
process,  which  is  not  liable  to  this  objection,  and  which  we  now 
proceed  to  describe. 

B,  Sulphuric  Acid. — The  operation  of  parting  with  sulphuric 
acid  was  first  suggested  by  M.  Diz^,  when  he  was  inspector  of 
the  French  mint.  In  the  Parisian  refineries,  gold  to  the  amount 
of  one-tenth  per  cent,  has  been  extracted  from  all  the  silver 
previously  parted  by  the  nitric  acid  process,  and  the  operation 
has  been  found  to  be  profitable. 

The  most  suitable  alloy  for  this  process  is  one  containing 
silver,  725 ;  gold,  200 ;  copper,  75.  Alloys  containing  more 
gold  are  protected,  to  a  certain  extent,  from  the  action  of  sul- 
phuric acid ;  those  which  have  more  copper  give  a  pasty  alloy, 
from  the  formation  of  an  anhydrous  sulphate,  which,  being 
insoluble  in  concentrated  sulphuric  acid,  prevents  the  action  of 
the  acid  on  the  alloy.  The  alloy  thus  prepared  is  put  in  a 
platinum  retort,  and  three  times  its  weight  of  concentrated  sul- 
phuric acid  is  poured  over  it.    The  alembic  is  then  covered  with 


296   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

its  head,  heat  applied,  and  the  operation  goes  on,  the  fumes  of 
sulphurous  acid  being  conducted  away  through  pipes,  which,  in 
some  factories,  open  into  the  chimney,  so  that  the  vapors  are 
carried  off.  This  acid  may  be  saved  by  reconverting  it  into 
sulphuric  acid,  by  means  of  nitrous  acid  fumes,  and  a  condensing 
apparatus ;  or  it  may  be  directly  made  use  of  by  conducting  it 
over  a  magma  of  lime,  as  in  the  gas-houses,  to  form  the  sulphite 
of  that  base.  The  production  of  this  sulphurous  acid  is  due  to 
the  deoxidation  of  the  oil  of  vitriol,  one  atom  of  its  oxygen  com- 
bining with  an  atom  of  silver,  while  the  resulting  oxide  combines 
with  the  sulphuric  acid  present,  to  be  converted  into  sulphate 
of  silver.  The  solution  goes  on  vigorously  with  a  copious  evo- 
lution of  sulphurous  acid  for  the  first  three  or  four  hours,  but 
afterwards  more  slowly,  and  the  operation  is  not  completed  till 
about  twelve  hours  more  have  elapsed. 

"When  the  solution  is  complete,  that  is  to  say,  when  all  the 
silver  has  been  converted  into  a  sulphate,  the  entire  contents  of 
the  alembic  are  emptied  into  water,  which  must  be  in  sufficient 
quantity  to  bring  the  liquid  to  50°  or  20°  B.  This  dissolves 
the  crystalline  sulphate  of  silver  which  had  sunk  to  the  bottom 
of  the  alembic  during  the  operation,  and  the  only  insoluble  mat- 
ter which  remains,  if  the  operation  has  been  properly  conducted, 
is  the  heavy  pulverulent  gold  which  subsides.  The  liquid  is 
now  decanted,  the  gold  repeatedly  and  thoroughly  washed,  the 
washings  being  of  course  emptied  into  the  same  vessel  with  the 
decanted  sulphate.  The  silver  is  precipitated  and  treated  as 
already  described  under  the  head  of  Nitric  Acid  Parting.  The 
gold  is  fused  with  a  little  nitre,  to  get  rid  of  any  copper  which 
may  have  escaped  the  acid,  and  the  melted  metal  poured  into  an 
ingot-mould. 

It  may  be  remarked  here  that,  in  concentrated  solutions,  the 
precipitation  of  the  silver  takes  place  very  slowly,  and  that  so- 
lutions of  sulphate  of  copper  which  have  a  specific  gravity  higher 
than  1.19  will  oxidate  the  silver.  The  solutions  of  sulphate  of 
copper  are  evaporated,  crystallized,  and  recrystallized.  The  acid 
mother  waters  are  evaporated  to  sp.  gr.  1.56,  55°  Baum^ ;  some 
anhydrous  sulphate  of  copper  precipitates,  and  the  supernatant 
acid  liquid  is  pure  enough  to  be  used  in  subsequent  operations. 


GOLD.  297 

The  boilers  in  -which  the  silver  is  precipitated  becomes  gradually 
coated  with  metal,  which,  when  scraped  off,  washed,  and  fused 
with  nitre,  yields  pure  silver. 

This  process  will  separate  from  silver  less  than  the  two- 
thousandth  part  of  gold.*  The  general  rule  of  the  French  re- 
finers is  to  retain  the  copper  and  the  gold  and  return  the  silver, 
when  the  alloy  contains  less  than  a  thousandth  of  gold.  When 
above  this  standard,  the  prices  vary  with  the  nature  of  the  alloy, 
averaging,  however,  about  fifty  cents  to  the  pound  troy. 

The  process  just  described  is  not  applicable  to  the  refining  of 
gold  bullion  or  any  mixture  of  gold  and  silver  containing  lead  or 
tin.  Independently  of  the  fact  that  lead  forms  an  insoluble 
salt  with  sulphuric  acid,  which  would  mix  with  and  contaminate 
the  gold,  the  presence  either  of  this  metal  or  of  tin,  in  company 
with  the  acid  liquor  in  the  platinum  alembic,  would  destroy  the 
precious  vessel  in  a  very  short  time.  These  metals  are  there- 
fore got  rid  of  at  the  beginning  by  fusion  with  nitre,  if  their 
proportion  be  small,  or  by  cupellation,  if  they  exist  in  large 
quantity. f 

*  Pettenkofer's  experiments  on  this  process,  as  quoted  by  Booth  and 
Morfit,  in  their  report  to  the  Smithsonian  Institution,  on  the  progress  of  the 
chemical  arts,  are  deserving  of  attention.  They  were  performed  at  the  re- 
finery in  Munich  on  kronenthaler  (crown-dollars),  which  contain  T5fi''iyo  o  of 
gold.  The  parting  is  rapid,  till  the  alloy  reaches  the  fineness  of  958  to  960 
thousandths  ;  after  which,  long-continued  boiling,  with  gieat  excess  of  acid, 
raises  it  to  only  970,  28  of  the  remaining  parts  being  silver,  and  2  plati- 
num. No  excess  of  acid,  even  with  repeated  boiling,  will  raise  the  stand- 
ard more  than  one-fourth  of  a  thousandth  above  this.  A  second  fusion  and 
parting  becomes  necessary.  lie  thinks  the  silver  is  alloyed  in  the  metallic 
state  with  the  gold,  but  that  it  does  not  exist  in  its  normal  condition. 
Sulphur  may  be  distilled  over  it,  but  it  gives  no  trace  of  sulphuret  of  silver. 
When  heated  with  boiling  sulphuric  acid  mixed  with  bichromate  of  potash, 
gold  is  dissolved  and  sesquioxide  of  chrome  is  formed  ;  but  neither  silver 
nor  platinum  is  attacked.  The  silver  may  be  extracted  by  fusion  with  bi- 
sulphate  of  soda  or  potassa.  The  great  preponderance  of  gold  seems  to 
assimilate  the  alloyed  silver  to  itself,  just  as  silver  renders  platinum  soluble 
in  nitric  acid,  or  platinum  causes  gold  to  be  corroded  when  fused  with 
nitre. 

f  For  a  fuller  description  of  the  French  establishments  for  parting,  and 
the  processes  there  adopted,  see  lire's  Dictionary  of  Arts  and  Manufac- 
tures and  Mines,  article  "Refining  of  Gold  and  Silver." 


298     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

C.  Jlqua  Regia. — The  separation  of  gold  and  silver  is  very 
conveniently  made  by  this  agent,  when  the  amount  acted  upon 
is  small  and  contains  but  little  silver  in  proportion  to  the  gold. 
It  is  not  suitable  for  large  operations,  as  the  acids  used  are  neces- 
sarily lost.  The  process  is  founded  upon  the  solubility  of  gold 
in  nitro-hydrochloric  acid,  and  the  insoluble  character  of  chloride 
of  silver. 

This  process  has  the  advantage  of  requiring  no  preliminary 
preparation  of  the  alloys.  All  that  is  necessary  for  its  success 
is,  that  the  gold  should  predominate  considerably  over  the  silver. 
Should  there  be  an  excess  of  silver,  the  chloride  which  forms 
will  protect  the  gold  from  the  action  of  the  acid.  This  diflS- 
culty  can  indeed  be  overcome  by  washing  off  the  acid,  dissolving 
the  chloride  of  silver  in  ammonia,  laminating  the  alloy,  and  re- 
applying the  solvent ;  but  this  operation  is  tedious  and  trouble- 
some, so  that  when  silver  is  present  in  excess,  it  is  much  better 
to  adopt  one  of  the  former  methods  of  parting. 

The  solvent  is  prepared  usually  by  mixing  from  one  to  two 
parts  of  nitric  acid  of  32°  B.  (sp.  gr.  1.28),  with  four  parts  hy- 
drochloric acid  of  22°  B.  (1.178.)  The  laminated  or  granulated 
alloy  is  introduced  into  this  and  digested  at  a  gentle  heat  till  all 
fumes  cease  to  pass  over.  At  first,  the  fumes  are  red  and 
heavy,  consisting  of  nitrous  acid,  but  towards  the  close  of  the 
operation  they  become  yellowish  or  greenish,  and  finally,  if  the 
heat  is  urged,  they  are  white.  At  this  period,  the  action  of  the 
acid  has  ceased.  The  liquid  is  then  poured  off,  a  fresh  supply 
of  acid  poured  on,  boiled  for  a  short  time,  and  then  decanted. 
The  remaining  chloride  of  silver  is  then  washed  and  reduced  by 
fusion  with  carbonate  of  potash,  or  by  reduction  with  metallic 
zinc  or  iron  in  the  humid  way.  The  gold  is  then  to  be  precipi- 
tated with  the  protosulphate  of  iron,  if  there  are  any  other 
metals  present ;  if  only  silver  was  in  the  alloy,  oxalic  acid  may 
be  used  as  a  precipitant. 

Simple  as  this  operation  appears,  some  precautions  are  neces- 
sary in  order  to  insure  success.  Great  care  must  be  taken  to 
rid  the  solution  of  any  excess  of  nitric  acid,  otherwise  the  preci- 
pitation with  sulphate  of  iron  will  be  difiicult,  the  gold  being 
redissolved  as  fast  as  it  is  precipitated.     This  is  effected  by 


GOLD.  299 

evaporation  to  dryness,  repeated  several  times,  with  the  addition 
of  hydrochloric  acid.  The  evaporation  must  be  conducted  over 
the  water-bath;  for,  should  the  heat  be  raised  above  212°  F.,  the 
terchloride  of  gold  will  be  reduced  to  metallic  gold  and  the  pro- 
tochloride.  Nitric  acid  being  completely  expelled,  the  protosul- 
phate  of  iron  is  added,  and  the  solution  is  allowed  to  stand  for 
twenty-four  hours.  It  is  better  to  have  the  precipitating  jar  well 
covered,  or  to  add  excess  of  hydrochloric  acid,  to  dissolve  the 
peroxide  of  iron  as  fast  as  it  is  formed.  When  the  precipitation 
is  ended,  the  liquid  is  decanted,  and  the  gold  thoroughly  washed, 
first  with  hydrochloric  acid,  then  with  acidulated  water,  and  then 
with  pure  water.  The  gold  is  then  fused  with  nitre  and  borax, 
and  cast  in  an  ingot-mould.  Precipitation  of  gold  by  copperas 
is  a  slow  process.  I  have  sometimes  obtained  the  metal  suffi- 
ciently pure  for  all  practical  purposes,  in  a  much  more  rapid 
manner  by  thoroughly  drying  the  chloride,  subjecting  it  to  a 
temperature  of  about  300°  F.  and  then  fusing  it  with  nitre. 

When  platinum  is  present,  the  process  of  parting  must  be 
modified.  Advantage  must  be  taken  of  the  property  possessed 
by  this  metal  of  becoming  soluble  in  nitric  acid  when  alloyed 
with  silver.  If  there  should  be  copper  present,  this  should  be 
removed  by  cupellation,  the  necessary  amount  of  silver  added, 
and  the  resulting  alloy  granulated  and  boiled  with  nitric  acid. 

The  standard  of  the  alloy  of  gold  is  expressed,  in  mercantile 
phraseology,  by  carats.  This  term  is  said  to  be  derived  from 
huara,  the  name  of  a  sort  of  bean,  the  fruit  of  a  species  of 
erythina,  in  the  province  of  Shangallas,  in  Africa.  This  name 
signifies,  in  the  jargon  of  the  natives,  the  sun,  the  tree  which 
bears  this  bean  producing  flowers  and  fruit  of  a  brilliant  flame 
color.  The  pods  of  this  plant,  being  nearly  uniform  in  their 
weight,  have  long  been  used  by  the  natives  in  weighing  gold-dust, 
which  is  sold  in  large  quantity  in  this  province.  From  Africa, 
say  the  etymologists,  from  whom  we  take  this  account,  the  beans 
were  exported  to  India,  where  they  were  used  for  weighing 
diamonds.  The  diamond  carat,  however,  differs  in  weight  from 
the  gold  carat.  The  former  weighs  four  nominal  grains,  each  of 
which  is  equivalent  to  .989  grain  troy.  The  gold  carat,  on  the 
other  hand,  which  is  also  applied  to  expressing  the  purity  of  al- 


300      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

loyecl  silver,  is  usually  a  mere  proportional  weight,  having  no 
definite  value.  Sometimes,  however,  a  definite  w^eight  is  spoken 
of  when  the  term  carat  is  used,  and  then  it  means  12  grains. 
When  the  proportional  carats  are  used,  the  entire  mass  is  sup- 
posed to  be  divided  into  24  parts,  each  of  which  is  a  carat. 
When  great  exactness  of  expression  is  required,  these  carats  are 
each  divided  into  32  parts,  so  that  the  entire  mass  is  divided  into 
768  32nds.  Absolutely  pure  gold,  of  course,  has  the  whole 
weight  of  the  mass  without  alloy,  and  is  therefore  said  to  be 
24  carats  fine,  or  simply  fine.  Should  the  mass  contain  one  part 
of  silver  or  other  metal,  it  will  be  called  23  carats  fine.  The 
mercantile  expression  for  the  fineness  of  gold,  therefore,  simply 
indicates  the  number  of  twenty-fourths  of  the  entire  mass, 
which  consist  of  the  pure  metal.  A  more  scientific  method,  how- 
ever, of  rating  these  is  to  express  the  proportion  of  the  pre- 
cious metal  in  thousandths.  Thus,  when  we  say  that  standard 
American  gold  has  the  fineness  of  900  thousandths,  we  mean 
that,  in  every  thousand  grains  of  the  coin  there  are  900  grains 
of  pure  gold,  the  remainder  being  a  variable  mixture  of  silver 
and  copper,  generally,  however,  in  the  proportion  of  25  to  75. 

GOLDBEATING. 

The  art  of  reducing  gold  to  fine  leaves  has  been  practised 
from  a  very  remote  antiquity.  The  Romans  were  in  the  habit 
of  using  it  in  ornamenting  their  houses,  and  Pliny  says  that  it 
was  hammered  out  so  as  to  cover  a  space  600  times  greater 
than  the  original  surface  cast.  Modern  workmen  have  carried 
the  lamination  of  gold  more  than  one  thousand  times  farther 
than  this. 

It  is  generally  supposed  that  it  is  essential  that  the  gold  em- 
ployed in  this  art  should  be  absolutely  pure.  This,  however,  is 
a  mistake.  In  fact,  there  is  very  little  goldleaf  to  be  found 
which  possesses  this  perfect  purity,  and  many  workmen  believe 
that  the  malleability  of  the  metal  is  increased  by  the  admixture 
of  alloy.  The  introduction  of  a  little  copper  or  silver  certainly 
increases  the  tenacity  of  the  leaf,  and  prevents  the  fine  lamince 
from  adhering  to  one  another,  a  property  possessed  by  the  pure 


GOLD.  301 

metal  in  a  remarkable  degree,  and  one  -which  is  very  troublesome 
to  the  goldbeater.  There  are  two  varieties  of  goldleaf,  the 
pale  and  the  deep  colored.  The  former  is  alloyed  ■with  silver 
alone,  the  latter  with  silver  and  copper.  Tints  between  these 
can  be  obtained  by  careful  management  of  the  alloy. 

The  gold  is  melted  with  nitre,  or  borax,  or  both,  in  a  crucible, 
and  cast  into  ingots,  the  size  of  which  varies  according  to  the 
mode  of  working  adopted  by  different  manufacturers.  They 
are  flat  and  oblong,  so  as  to  be  of  convenient  form  for  lamina- 
tion. The  French  goldbeaters  forge  this  ingot,  annealing  it 
from  time  to  time,  as  they  find  it  becoming  hard  and  disposed  io 
crack.  The  ingots,  or  portions  of  them,  of  suitable  size,  are  noV 
passed  through  a  laminating  machine,  consisting  of  two  very 
fine,  hard,  polished  steel  rollers,  with  the  necessary  apparatus 
for  adjusting  the  distance  between  them.  The  width  of  the 
metallic  strip  remains  unaltered,  and  the  flatting  is  carried  on 
entirely  at  the  expense  of  its  longitudinal  diameter,  so  that -it  is 
at  last  reduced  to  a  long  ribbon  not  more  than  jl^  of  an  inch  in 
thickness.  This  ribbon  is  now  annealed  in  the  fire,  and  then 
cut  up  in  pieces  of  about  an  inch  square,  which  are  introduced 
into  a  packet  made  of  leaves  of  fine  vellum,  or  of  prepared  ani- 
malized  paper,  so  that  the  metal  and  the  vellum  alternate.  This 
packet  is  enveloped  in  a  strong  parchment  case,  and  is  then 
ready  for  the  operation  of  beating. 

The  beating  is  performed  with  a  hammer,  of  about  sixteen 
pounds'  weight,  on  a  solid  smooth  block  of  marble,  strongly 
framed,  and  surrounded  by  a  raised  wooden  ledge,  and  having  a 
leathern  apron  in  front  to  catch  any  scattered  fragments  of  the 
precious  metal.  The  hammer  is  short-handled,  and  is  worked 
with  one  hand.  The  elasticity  of  the  packet  causes  the  hammer 
to  rebound,  and  saves  labor,  by  obviating  the  necessity  of  lifting 
so  great  a  weight.  Every  now  and  then,  in  the  interval  between 
two  blows,  the  packet  is  turned,  so  as  to  be  equally  beaten  on 
both  sides.  The  blow  is  struck  directly  in  the  middle  of  the 
packet,  and  the  hammer  is  slightly  convex,  that  it  may  compress 
the  gold  most  in  the  centre  and  dispose  it  equally  on  either  side. 
The  workman  withdraws  the  packet  from  time  to  time  to  cool  it, 
as  the  heat  developed  by  these  continual  heavy  blows  would  in- 


302      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

jure  the  skin;  and  he  works  it  backward  and  forward  to  over- 
come any  adhesions  between  the  gold  and  the  vellum.  At  in- 
tervals the  packet  is  opened,  to  see  that  everything  is  going  on 
satisfactorily,  and  the  leaves  are  occasionally  shifted,  that  all 
may  be  uniformly  compressed.  The  beating  is  continued  till  the 
leaves  have  reached  the  edge  of  the  packet,  or  till  the  one  inch 
squares  cover  each  a  space  of  four  inches  square. 

The  result  of  this  first  beating  is  gold  foil,  which  is  cut  evenly 
and  put  into  books,  weighed  and  numbered.  The  numbers  run 
from  4  to  36,  and  indicate  the  number  of  grains  which  each  leaf 
weighs. 

Should  the  beating  go  on  to  the  manufacture  of  leaf,  these 
products  of  the  first  beating  are  taken  out,  laid  on  a  leathern 
cushion,  and  cut  each  into  four  parts  with  a  knife.  Each  of 
these  parts  is  introduced  into  another  packet  of  goldbeater's- 
skin  or  prepared  ox-gut,  and  beaten  in  the  same  manner  as  be- 
fore with  a  hammer  weighing  from  ten  to  twelve  pounds,  till 
they  expand  to  the  size  of  the  packet. 

After  this  second  beating,  the  leaves  are  again  removed  and 
quartered  by  a  piece  of  sharp-edged  cane,  as  they  have  a  tend- 
ency to  adhere  to  a  steel  knife.  They  are  replaced  in  a  packet 
as  before,  and  again  beaten  out  nearly  to  its  diameter.  The 
gold  has  now  reached  such  an  attenuation  that  100  square  feet 
of  it  will  only  weigh  an  ounce.  It  can  be  beaten  out  thinner  even 
than  this,  and  an  ounce  made  to  cover  IGO  square  feet,  but  the 
process  is  tedious  and  wasteful  from  the  number  of  broken  leaves, 
and  attended  by  no  corresponding  advantage. 

The  thin  leaves  are  now  taken  out  of  the  packets  with  wooden 
pliers,  and,  by  means  of  the  breath,  blown  flat  on  a  cushion,  an 
operation  requiring  the  dexterity  of  long  practice.  The  broken 
leaves  are  rejected,  and  the  rest  are  cut  to  a  uniform  size  with  a 
sharp  cane,  which  reduces  them  to  3  or  3|  inches  square.  They 
are  then  transferred  to  little  books,  the  leaves  of  which  have  been 
covered  with  red  chalk,  to  prevent  the  metal  from  adhering. 
Each  book  usually  contains  25  leaves  of  gold.  The  average 
thickness  of  ordinary  goldleaf  is  ogi'ooo  of  an  inch. 


GOLD.  303 


ALLOYS   AND   NON-SALIjSTE   COMPOUNDS. 

Gold. — Gold  varies  in  its  appearance,  in  accordance  with  the 
method  by  which  it  has  been  obtained.  The  precipitate  by 
protosulphate  of  iron  is  a  dark-brown  powder ;  that  by  oxalic 
acid  has  a  yellower  tint,  and  here  and  there  a  metallic  lustre ; 
while  the  gold  obtained  by  evaporating  the  terchloride  at  300° 
is  in  spongy  masses  of  a  dull  yellow  tint,  resembling,  in  some  de- 
gree, what  is  known  to  artisans  as  deadened  gold,  though  even 
less  lustrous  than  that.  The  metal  obtained  by  2>cirtmg  has  a 
loose  spongy  texture,  and  a  reddish  tint.  By  annealing  in  a 
muffle  below  the  point  of  fusion,  this  dull  tint  leaves  it ;  it  con- 
tracts greatly  and  assumes  a  yellow  metallic  lustre.  In  all 
these  states  gold  is  capable  of  being  welded  by  simple  pressure. 

A  substance  has  recently  been  prepared  for  the  use  of  dentists, 
under  the  title  of  crystallized  or  sponge  gold.  The  first  term 
is  inappropriate,  as  there  is  often  nothing  of  the  crystalline 
character  about  it.  The  material  presents  very  different  appear- 
ances. That  imported  from  Europe  is  in  small  porous  masses 
of  a  dull  yellow  or  reddish-yellow  tint.  Again,  it  is  found  in 
small  ovoid  lumps,  also  porous,  but  tolerably  resistant,  though 
readily  welding  under  pressure.  A  third  variety  is  in  cakes 
made  of  fine  filaments  of  lustrous  gold.  This  form  has  a  greater 
tenacity  than  either  of  the  preceding  varieties. 

The  preparation  of  this  article  has  been  kept  profoundly 
secret.  I  have  experimented  upon  it,  and  succeeded  in  imitat- 
ing it.  A  preparation,  much  resembling  it,  may  be  made  by 
simply  annealing  the  gold  obtained  from  alloy  by  the  process  of 
parting.  It  may  also  be  imitated  by  decomposing  the  dry  ter- 
chloride at  a  high  temperature,  and  then  annealing  the  resulting 
cake  at  a  dull  red  heat.  The  gold  from  which  mercury  has  been 
distilled,  after  the  process  of  amalgamation,  also  resembles  the 
sponge  gold.*  In  all  these  preparations,  it  is,  of  course,  neces- 
sary to  be  absolutely  certain  of  the  purity  of  the  metal. 

*  Since  the  above  was  written,  the  author  has  seen  the  formula  of  the 
New  York  patentee. 

He  amalgamates  the  gold  with  from  4  to  12  times  its  weight  of  mercury, 
triturates,  heats  to  about  180°  F.,  and  allows  it  to  stand  for  several  hours. 


804      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Solid  gold,  whether  molten  or  welded,  is  universally  known 
by  its  brilliant  yellow  color.  It  is  capable  of  receiving  a  very 
high  lustre,  but  is  inferior  in  brilliancy  to  steel,  silver,  and  mer- 
cury. When  pure,  it  is  so  soft  that  it  cannot  be  made  up  into 
jewellery  or  other  articles  to  any  advantage.  It  tarnishes 
readily,  because  it  is  so  easily  scratched,  and  wears  away  rapidly 
for  the  same  reason.  In  ductility  and  malleability,  it  excels  all 
other  metals.  A  single  grain  may  be  drawn  into  a  wire  500 
feet  long,  or  hammered  into  leaves  of  more  than  50  square 
inches  in  superficial  extent,  and  one  three  hundred  thousandth 
of  an  inch  in  thickness.  The  specific  gravity  of  gold  varies. 
The  molten  metal  has  a  density  of  19.26,  while  the  hammered 
ranges  from  19.4  to  19.65.  Gold  fuses  at  2016°,  according  to 
Daniell,  with  considerable  expansion,  and  on  cooling  contracts 
more  than  any  other  metal. 

Gold  has  a  very  feeble  affinity  for  oxygen.  No  length  of 
exposure,  no  amount  of  heat  is  sufficient  to  force  it  to  combine 
with  oxygen.  When  ignited  in  oxygen  gas,  or  by  a  current  of 
electricity,  or  by  the  oxyhydrogen  blowpipe,  it  is  dissipated  in 
the  form  of  a  purple  powder,  which  has  been  supposed  by  some 
to  be  an  oxide,  though  others  will  have  it  to  be  nothing  but  finely 
divided  gold.  The  last  opinion  is  rendered  probable  by  the  fact 
that  the  presence  of  oxygen  is  not  necessary  for  the  production 
of  this  so-called  purple  oxide,  it  being  produced  by  ignition  in 
an  atmosphere  of  hydrogen. 

Not  only  is  gold  difficult  to  oxidate,  but  it  is  also  scarcely  pos- 
sible to  volatilize  it.  The  heat  of  a  blast  furnace  only  fuses  it, 
without  loss  of  weight,  and  it  is  only  with  great  difficulty  that 
it  is  dissipated  in  the  powerful  heat  of  the  oxyhydrogen  blowpipe. 

It  is  insoluble  in  the  simple  acids,  no  matter  how  concentrated 
they  may  be.  Of  the  metalloids,  it  is  readily  soluble  in  chlorine 
and  fluorine.  Aqua  regia,  or  nitro-hydrochloric  acid,  readily 
dissolves  it.  This  action  is  in  all  probability  due  to  chlorine,  a 
mixture  of  nitric  and  hydrochloric  acids  being  a  constant  source 
of  that  gas,  so  long  as  they  mutually  decompose  each  other. 

He  then  treats  it  with  nitric  acid,  in  the  manner  already  described  under 
the  head  of  parting  gold  and  silver.  Finally,  he  anneals  the  residual  gold 
at  a  heat  just  short  of  the  fusing-point  of  gold. 


GOLD.  305 

Nitrofluoric  acid  is  also  a  solvent  of  gold,  fluorine,  in  like  manner, 
beinof  the  active  ingredient. 

The  symbol  of  gold  is  Au,  its  combining  number  199.207  on 
the  hydrogen,  and  1243.613  on  the  oxygen  scale.  Berzelius 
regards  it  as  Aug;  its  combining  number,  on  this  hypothesis, 
would,  therefore,  be  99.604  on  the  hydrogen  scale. 

Protoxide  of  Grold. — AuO.  207.22.  When  the  peroxide  or 
perchloride  of  gold  is  boiled  with  a  solution  of  caustic  or  carbon- 
ated fixed  alkalies,  or  when  the  terchloride  is  precipitated  by 
dinitrate  of  mercury,  there  remains  a  dark-green  or  violet 
powder,  which  does  not  combine  with  acids,  and  which  is  resolved 
by  hydrochloric  acid  into  terchloride  and  metallic  gold.  It  is 
most  conveniently  obtained  by  treating  protochloride  of  gold 
with  a  cold  solution  of  caustic  potash.  In  consequence  of  a 
series  of  decompositions,  chloride  of  potassium  makes  its  appear- 
ance in  the  solution,  and  the  oxygen  of  the  potash  is  transferred 
to  the  gold.  The  oxide  thus  obtained  is  of  an  olive-green  color, 
partially  soluble  in  the  alkaline  solution,  and  spontaneously 
decomposable,  being  resolved  into  terchloride  and  metallic  gold. 

Peroxide  of  Crold. — AuOj,  223.24.  This  is  also  known  as 
teroxide  of  gold  and  auric  acid.  It  may  be  obtained  by  digest- 
ing the  terchloride  with  a  slight  excess  of  magnesia  or  oxide  of 
zinc,  which  throws  down  nearly  all  the  gold  with  magnesia  or 
zinc.  The  precipitate  is  washed  with  water  and  digested  with 
strong  nitric  acid,  which  dissolves  the  magnesia  or  zinc,  together 
with  some  gold,  leaving  a  brown  anhydrous  oxide.  Digestion 
with  dilute  nitric  acid  furnishes  a  reddish  hydrated  oxide. 
Another  method  of  preparing  it,  is  to  dissolve  one  part  of  gold 
in  the  usual  way,  to  render  it  quite  neutral  by  evaporation,  and 
redissolve  in  twelve  parts  of  water.  One  part  of  carbonate  of 
potassa,  dissolved  in  twice  its  weight  of  water,  is  then  added, 
and  the  whole  digested  at  about  170°.  Carbonic  acid  escapes 
and  the  hydrated  peroxide  subsides  as  a  brownish-red  precipi- 
tate. It  is  now  thoroughly  washed,  dissolved  in  pure  nitric 
acid  of  specific  gravity  1.4,  and  the  solution  decomposed  by 
water.  The  hydrated  peroxide  is  thus  obtained  in  a  state  of 
purity,  and  is  rendered  anhydrous  by  a  temperature  of  212°. 

This  oxide  is  yellow  when  hydrated,  and  black  when  anhy- 
20 


306      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

drous.  It  retains  its  oxygen  with  a  very  feeble  attraction,  so 
that  it  may  be  decomposed  at  a  heat  below  redness.  Indeed,  it 
is  spontaneously  reduced,  though  not  completely,  when  kept  in 
the  dark,  and  loses  all  its  oxygen  on  exposure  to  sunlight. 
Hydrochloric  acid  dissolves  it  readily,  forming  the  common 
solution  of  gold.  Nitric  and  sulphuric  acids  also  dissolve,  but 
seem  to  form  no  definite  compound  with  it,  as  it  is  easily  pre- 
cipitated from  these  solutions  by  the  addition  of  water. 

According  to  the  experiments  of  Pelletier,  this  oxide  behaves 
very  differently  towards  the  alkalies.  In  solutions  of  potassa 
and  baryta  it  is  dissolved,  apparently  forming  regular  salts,  in 
which  the  oxide  plays  the  part  of  a  weak  acid.  This  chemist, 
therefore,  denied  that  the  teroxide  of  gold  is  a  salifiable  base, 
and  transferred  it  to  the  acids,  under  the  title  of  auric  acid,  its 
salts  being  called  aurates. 

When  the  teroxide  is  kept  in  a  strong  solution  of  ammonia 
for  a  day,  fulminating  gold  of  a  deep  olive  color  is  generated. 
A  similar  compound  is  obtained  by  precipitating  the  terchloride 
of  gold  with  ammonia,  and  digesting  the  resulting  precipitate 
with  the  precipitant  in  excess.  The  precipitate  is  a  bright 
opaque  gold  yellow,  and  consists  of  fulminating  gold  with  double 
chloride  of  ammonium  and  the  metal.  This  compound  may  be 
dried  at  212°;  but  friction  or  a  heat  of  290°  immediately  pro- 
duces an  explosion.  It  is  best  made  in  small  quantities  and 
dried  in  the  open  air. 

The  results  of  the  detonation  are  metallic  gold,  water,  nitro- 
gen, and  ammonia.  Dumas's  analyses  indicated  its  composition 
to  be  one  equivalent  of  gold,  six  of  hydrogen,  two  of  nitrogen, 
and  three  of  oxygen,  or  AujNgHgOj.  He  expressed  its  composi- 
tion by  the  formula  AuN,  +  H3N+  3H0 ;  that  is,  he  regarded  it  as 
a  hydrated  nitruret  of  gold  with  ammonia.  Turner  considers  it 
to  be  a  diaurate  of  ammonia,  and  expresses  it  by  the  formula 
2NH3AUO3. 

Purple  Oxide. — It  has  already  been  said  that  there  were 
grave  doubts  of  the  propriety  of  the  term  oxide  applied  to  this 
substance.  This  question  will  be  discussed  more  at  large  under 
the  next  head.  Purple  of  Cassius.  In  favor  of  the  opinion  that 
the  so-called  purple  oxide  is  only  metallic  gold  in  a  state  of  fine 


GOLD.  307 

subdivision,  it  may  be  urged  that  every  tyro  in  chemistry  knows 
that,  when  a  precipitant  of  metallic  gold  is  added  to  very  dilute 
solutions  of  this  metal,  its  first  effect  is  to  communicate  a  bright 
purple  tint  to  the  whole  fluid.  Besides,  the  heat  to  which  this 
substance  is  subjected  in  the  glass-stainer's  establishment,  ought 
to  discharge  any  combined  oxygen.  Berzelius,  however,  advo- 
cated the  opinion  that  there  is  an  intermediate  oxide  between 
the  protoxide  and  the  teroxide,  founding  his  arguments  upon 
the  analogies  of  the  oxides  of  silver. 

Pujyle  of  Cassius. — This  unintelligible  preparation  of  gold 
is  much  employed  by  the  porcelain  manufacturer,  the  manu- 
facturer of  colored  glass,  and  the  dentist,  to  give  various  tints 
of  red  and  pink  to  their  wares.  The  preparation  of  this  exqui- 
site pigment  is  a  matter  of  great  nicety,  and  sometimes  the  most 
experienced  manufacturers  are  disappointed  in  their  results. 

When,  into  a  weak  solution  of  terchloride  of  gold,  protochlo- 
ride  of  tin,  acidulated  with  a  few  drops  of  nitric  acid,  is  let 
fall,  a  purple  tint  is  communicated  to  the  entire  solution.  With 
care  a  precipitate  may  be  obtained.  It  must  be  observed,  how- 
ever, that  success  depends  entirely  upon  hitting  the  exact  con- 
dition of  the  tin  and  the  gold.  The  chloride  of  the  latter  must 
be  neutral  and  free  from  nitric  acid  ;  that  of  the  former  must  be 
a  due  mixture  of  the  perchloride  and  the  protochloride.  The 
protochloride  of  tin  alone  is  a  powerful  deoxidating  reagent, 
and  throws  down  a  brown  precipitate  of  gold-tin ;  the  perchlo- 
ride affords  no  precipitate  whatever  ;  but  a  neutral  solution,  of 
one  part  crystallized  protochloride  of  tin,  with  two  parts  crystal- 
lized perchloride  of  tin,  throws  down  from  a  solution  of  one  part 
crystallized  terchloride  of  gold,  the  purple  precipitate  required. 
According  to  Fuchs,  a  solution  of  the  sesquixode  of  tin  in  hy- 
drochloric acid,  or  of  the  sesquichloride  in  water,  which  is  the 
same  thing,  accomplishes  the  same  result  when  dropped  in  a 
properly  dilute  solution  of  gold. 

As  this  is  an  important  article  to  the  dentist,  several  different 
formulae  for  obtaining  it  are  here  inserted. 

Fuchs  recommends  manufacturers  to  add  to  a  solution  of  ses- 
quichloride of  iron  a  solution  of  protochloride  of  tin  till  the 
iquid  assumes  a  pale-green  tint.     The  reaction  here  consists  in 


308      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

the  abstraction,  from  the  sesquichloride  of  iron,  half  an  atom  of 
chlorine,  which  unites  with  the  chlorine  of  the  tin  salt,  con- 
verting that  compound  into  a  sesquichloride,  while  the  iron  is 
left  in  the  state  of  protochloride,  which  is  a  pale  sea-green  salt. 
Add  to  the  solution  thus  obtained  a  properly  dilute  solution  of 
terchloride  of  gold  which  has  been  freed  from  nitric  acid.  A 
very  fine  precipitate  of  purple  of  Cassius  falls,  and  the  protochlo- 
ride of  iron  remains  in  solution.  The  purple  thus  prepared  is 
said  to  keep  a  long  time  in  the  air  without  alteration.  Mercury 
does  not  abstract  from  it  the  smallest  particle  of  gold. 

Berzelius  dissolved  gold  in  aqua  regia,  expelled  all  the  nitric 
acid  in  the  manner  already  described,  and  then  diluted  largely 
with  water.  He  ascertained  the  proper  point  of  dilution  by  dip- 
ping a  glass  rod  in  a  solution  of  sesquichloride  of  tin,  and  then 
into  the  gold  solution,  and  adding  water  till  the  precipitate  re- 
dissolved  by  agitation.  He  then  added  a  solution  of  sesquichlo- 
ride of  tin  portion-wise,  stirring  the  liquid  after  each  addition, 
till  the  chloride  of  gold  was  all  decomposed.  The  brown  or 
purple  liquid  then  deposited  the  purple  after  standing  for  twenty- 
four  hours.  Care  must  be  taken,  in  following  this  method,  not 
to  add  an  excess  of  the  tin  salt. 

Buisson's  formula  is  as  follows :  Dissolve  1  gramme*  of  the 
best  tin  in  a  sufficient  quantity  of  hydrochloric  acid  to  make  a 
neutral  solution.  Dissolve  2  grammes  of  tin  in  aqua  regia,  com- 
posed of  3  parts  nitric  to  1  part  hydrochloric  acid,  and  warm  it, 
that  no  protochloride  may  remain  in  solution.  Then  dissolve 
7  grammes  of  pure  gold  in  aqua  regia,  composed  of  1  part  nitric 
and  6  parts  hydrochloric  acid,  taking  care  to  make  the  solution 
neutral.  Dilute  the  last  solution  with  3  J  litres  (about  3  quarts) 
of  water,  and  add  to  it  the  perchloride  of  tin,  and  after  that  the 
protochloride,  drop  by  drop,  till  the  precipitate  assumes  the 
desired  color.     "Wash  the  precipitate  as  quickly  as  possible. 

Another  formula  requires  the  operator  to  warm  10  parts  of 
perchloride  of  tin  and  ammonium  with  1.07  parts  of  tin  and  40 
of  water,  till  the  tin  is  all  dissolved;  then  add  140  parts  of 
water,  and  add  it  to  a  solution  of  1.34  parts  of  gold  in  aqua 

*  A  gramme  is  15.43-i  grains. 


GOLD.  309 

regia,  diluted  with  48  parts  of  water,  as  long  as  a  precipitate 
falls.  Wash  and  dry  the  resulting  purple  at  a  temperature  of 
212°. 

The  French  Pharmacopoeia  orders  10  parts  of  chloride  of  gold 
to  be  dissolved  in  2,000  parts  of  distilled  water.  To  this  is  to 
be  gradually  added,  as  long  as  a  precipitate  falls,  a  solution  of 
10  parts  of  pure  tin  in  20  of  hydrochloric  acid.  The  precipitate, 
after  subsidence,  is  washed  by  decantation,  filtered  and  dried  at 
a  very  gentle  heat. 

The  same  substance  is  more  easily  obtained  by  fusing  together 
150  parts  of  silver,  20  of  gold,  and  35.1  of  tin,  and  dissolving 
out  the  first-named  metal  with  nitric  acid.  In  order  to  avoid 
loss  of  tin  by  oxidation,  it  is  best  to  granulate  the  three  metals, 
and  then  to  throw  them  into  a  redhot  black-lead  crucible  con- 
taining a  little  borax. 

Prick's  prescription  is :  Let  tin  be  digested  in  very  dilute 
aqua  regia  without  heat,  till  the  fluid  becomes  faintly  opalescent, 
when  the  metal  must  be  taken  out  and  weighed.  The  liquor  is 
to  be  diluted  largely  with  water,  and  a  definite  weight  of  a 
dilute  solution  of  gold,  and  dilute  sulphuric  acid,  are  to  be 
simultaneously  stirred  into  the  nitro-muriate  of  tin.  The  solu- 
tions must  be  so  managed  that  the  gold  in  the  one  shall  be  to 
the  tin  in  the  other  in  the  proportion  of  36  to  10. 

The  description  of  the  methods  of  obtaining  this  substance 
have  been  thus  minutely  given,  because  it  is  an  invaluable  ma- 
terial to  the  manufacturer  of  incorruptible  teeth.  The  common 
name  by  which  it  is  known  to  him  is  gum-color. 

The  precipitate  when  recently  made  is  a  brownish-purple  or 
deep  violet  color,  soluble  in  water  of  ammonia,  with  a  deep  purple 
color,  from  which  it  is  precipitated  by  acids  or  heat.  The  color 
is  usually  changed  by  this  precipitation,  and  assumes  more  of  a 
blue  tint.  When  the  ammoniacal  solution  is  heated  to  140°  or 
176°,  in  a  close  flask,  it  deposits  purple  rapidly  without  redis- 
solving  it ;  on  evaporation,  the  precipitate  is  found  to  have 
changed  its  character,  though  its  appearance  is  the  same.  It 
is  now  insoluble  in  ammonia.  The  solution  gradually  decom- 
poses in  the  light,  depositing  metallic  gold.  The  purple  preci- 
pitate becomes  brighter  when  dry,  but  still  has  a  brownish  tint, 


310      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

resembling,  more  nearly  than  anything  else,  a  dirty  and  faded 
episcopal  purple. 

The  chemical  nature  of  this  remarkable  compound  still  re- 
mains a  problem.  According  to  Berzelius,  its  sole  loss  when 
heated  to  redness  is  7.65  per  cent,  of  water,  and  the  residue  has 
a  brick-red  tint,  arising,  it  has  been  supposed,  from  a  mixture 
of  metallic  gold  and  binoxide  of  tin.  Fusion  with  nitre  converts 
it  into  stannate  of  potassa  and  an  alloy  of  gold  and  tin.  Nitro- 
hydrochloric  acid  dissolves  out  the  gold  and  some  of  the  tin, 
leaving  peroxide  of  tin.  The  action  of  mercury  is  variously 
stated.  Some  chemists  say  it  has  no  eflfect  upon  the  compound, 
and  others  that,  at  a  temperature  of  from  212°  to  300°  F.,  it 
dissolves  out  all  the  gold.  Fuchs's  precipitate  loses  no  gold  on 
the  addition  of  mercury. 

The  proportions  of  the  different  ingredients  are  variously 
stated  by  different  authors.  The  following  table  will  give  an 
idea  of  these  variations  : — 


Gold. 

0- 

side  of  tin 

Oberkampf, 

purple 

precipitate     . 

39.82 

60.18 

(( 

violet 

(; 

20.58 

79.42 

Berzelius    . 

. 

,            , 

30.725 

69.275 

Buisson 

, 

.            , 

30.19 

69.81 

Gay  Lussac 

. 

, 

30.89 

69.11 

Fuchs 

, 

,            , 

17.87 

82.13 

The  opinions  entertained  by  different  chemists  of  the  actual 
constitution  of  this  precipitate  differ  still  more  widely.  Thus  it 
has  been  called  a  terstannate  of  the  protoxide  (AuO,3Sn02+4 
HO)  with  42.5  per  cent,  of  gold ;  a  hexa-stannate  of  the  pro- 
toxide (AuO,6Sn02X  6H0)  with  28  per  cent,  of  gold;  a  proto- 
stannate  of  tin  and  gold  (SnO,3Sn02  +  AuO,2Sn02  +  6HO) ;  a 
stannite  of  the  deutoxide  of  gold  (purple  oxide)  Au02,2Sn203  +  - 
4H0)  with  39  per  cent,  of  gold,  and  this  is  the  view  of  its  com- 
position adopted  by  Berzelius ;  or,  finally,  a  sesquixode  of  tin 
and  stannate  of  the  deutoxide  of  gold  (2  (SnO,Sn02)  +  Au02,- 
2Sn02  +  6HO)  Avith  28  per  cent,  of  gold. 

It  is  manifest  that  the  purple  precipitate  of  Cassius  cannot  be 
a  mere  mechanical  admixture  of  its  ingredients,  because  its 
color  is  changed  in  a  manner  that  mere  admixture  could  never 


GOLD.  311 

effect ;  and,  farther,  because  it  is  soluble  in  ammonia.  It  has  been 
argued  that,  as  mercury  extracts  nothing  from  the  carefully  made 
purple,  the  gold  must  be  oxidated  ;  and  that,  as  the  precipitate 
is  thrown  down  from  the  terchloride  of  gold  by  the  protochloride 
of  tin,  and  not  at  all  by  the  perchloride  of  this  metal,  it  must 
be  in  a  low  state  of  oxidation ;  and,  farther,  that,  as  a  stannate 
of  the  protoxide  would  probably  lose  oxygen,  when  heated, 
■which  the  purple  does  not,  it  is  most  probably  either  a  stannate 
or  a  stannite  of  the  purple  oxide. 

This  precipitate,  when  fused  with  vitreous  substances,  such  as 
flint-glass,  or  sand  and  borax,  yields  a  purple  enamel,  which  is 
used  for  giving  a  purple  or  pale-red  tint  to  porcelain  and  glass. 
The  depth  of  the  tint  depends  very  much  upon  the  management 
of  the  frit,  as  will  be  hereafter  explained.  It  has  been  sup- 
posed to  be  a  compound  of  the  purple  oxide  of  gold  with  the 
earthy  matters  of  the  flux. 

Protosulplturet  of  Gold. — AuS.  215.3.  When  sulphuretted 
hydrogen  is  passed  through  a  boiling  solution  of  terchloride  of 
gold  a  dark  powder  subsides,  containing  one  atom  of  sulphur  in 
combination  with  one  atom  of  gold.  It  is  black,  with  a  dark- 
brown  streak,  and  contains  92.5  per  cent,  of  metal. 

Tersulphuretof  Crold. — AuSj.  247.5.  Sulphuretted  hydrogen 
passed  in  a  stream  through  a  cold  solution  of  the  terchloride, 
throws  down  a  black  tersulphuret  of  gold.  When  formed  by 
precipitating  the  sulphauride  of  potassium  with  acids,  it  is 
yellow.  Both  sulphurets  are  decomposed  by  heat,  the  sulphur 
being  driven  off,  and  metallic  gold  left.  The  persulphuret 
dissolves  readily  in  sulphuret  of  potassium,  and  acts  as  a  sulph- 
acid  to  the  other  positive  sulphurets,  and  as  a  sulpho-base  to  the 
negative  sulphurets  of  arsenic,  molybdenum,  &c.  The  sulpho- 
carbonate,  AuS^,  SCSj,  is  a  black  precipitate  formed  by  bringing 
together  the  solutions  of  the  terchloride  of  gold  and  the  sul- 
phuret of  carbon. 

Pliosphuret  of  gold  is  a  whitish  metallic  compound,  more  fusible 
and  more  brittle  than  gold.  It  is  made  by  direct  combination 
or  by  heating  gold  with  phosphoric  glass  and  charcoal.  When 
heated  in  the  air,  phosphorus  burns  off. 


312      CHEMISTKT  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


ALLOYS  OF  GOLD. 

Gold  readily  combines  with  most  of  the  metals,  forming 
alloys  of  various  colors,  and  various  degrees  of  hardness,  tough- 
ness, and  malleability.  Pure  gold,  as  has  already  been  said,  is 
too  soft  for  the  purposes  of  the  workman  in  this  precious  metal. 
The  principal  base  metal  used  to  alloy  it,  is  copper. 

Of  the  alloys  with  the  rarer  metals,  it  is  not  necessary  to  say 
much  in  this  place.  It  is  well  enough,  however,  to  advert  to 
those  with  arsenic  and  antimony,  because  these  are  contamina- 
tions which  may  very  readily  jBnd  their  way  into  the  gold  prepared 
by  the  dentist  for  his  plate-work,  or  into  that  which  he  obtains 
from  the  jeweller's  scraps  and  the  sweepings  of  his  own  room. 

Arsenic,  even  in  vapor,  forms  a  gray,  brittle  alloy  with  gold, 
containing  04 y  of  arsenic,  which  cannot  be  wholly  expelled 
by  two  hours'  fusion  in  an  open  crucible.  Arsenic  in  the  pro- 
portion of  Tj  J  ^  renders  gold  brittle  without  changing  its  color. 
The  alloy  with  -^  of  antimony  is  pale  and  brittle,  and  gives  up 
its  antimony  by  heat;  and  y^^^  of  antimony  is  sufficient  to 
destroy  the  malleability  of  gold. 

The  alloys  with  the  platinoid  metals  are  brittle  and  pale, 
unless  the  gold  is  in  considerable  excess.  With  palladium,  gold 
forms  a  hard  pale  alloy,  6  parts  of  gold  to  1  of  palladium  being 
nearly  white.  The  gold  ores  of  Gongo  Seco,  in  Brazil,  contain 
this  substance  in  sufficient  quantity  for  separation  on  the  large 
scale.  Iridium  is  said  to  form  a  yellow-ductile  alloy  with  gold, 
probably  through  the  agency  of  copper,  with  which  it  forms  a 
fusible  and  malleable  alloy.  Pure  iridium  is  the  most  refractory 
of  all  metals,  Berzelius  having  failed  to  fuse  it,  and  Mildren 
having  succeeded  with  diiBculty,  by  the  use  of  his  powerful 
batter  .  Bunsen  and  Hare  have  also  fused  it.  Iridium  is 
sometimes  found  in  combination  with  the  scraps  of  native  gold 
from  alluvial  washings.  Its  sharp,  hard  crystals  are  infusible  at 
any  working  temperature,  so  that  they  must  be  picked  out  care- 
fully before  the  gold  is  melted,  or  they  will  render  it  impossible 
to  work  the  softer  metal. 

It  must  be  borne  in  mind,  however,  that  in  this  manner  only 
the  coarse  particles  are  removed.     There  remain  finer  crystals, 


GOLD,  313 

■which  are  very  troublesome.  In  California  gold,  this  substance 
is  occasionally  very  annoying  to  those  who  fuse  it  directly, 
and  sometimes,  from  the  extreme  hardness  of  the  crystals, 
materially  injures  the  rolls  used  in  milling  out  plate-work.  It 
is  necessary,  therefore,  to  resort  to  the  operation  of  parting. 
The  iridosmin  of  California  contains  the  new  metal  ruthenium. 

The  alloy,  with  'platinum,  renders  gold  pale,  but  does  not 
diminish  its  malleability,  unless  it  forms  a  large  proportion  of 
the  alloy.  When  united  with  silver  it  may,  as  has  already  been 
said,  under  the  head  of  parting,  be  dissolved  out  with  nitric 
acid.*  Rhodium  forms  malleable  alloys  with  gold.  In  Mexico, 
it  has  been  found  alloying  the  native  gold  in  considerable  quan- 
tity, averaging  31  per  cent,  of  the  compound. 

Lead  and  bismuth  are  alike  destructive  to  the  malleability  of 
gold.  An  alloy  composed  of  only  one  part  of  either  of  these 
metals  and  1,920  parts  of  gold  is  brittle.  The  mode  of  separa- 
tion has  already  been  pointed  out  under  the  head  of  metallurgic 
treatment  of  alloys. 

Zino  hardens  gold,  as  well  as  whitens  it,  and  enters  as  an 
ingredient  in  various  compounds  made  by  the  goldsmith.  Eleven 
parts  of  gold  to  one  of  zinc  make  an  alloy,  pale,  greenish-yellow, 
and  brittle.  Equal  parts  of  gold  and  zinc  produce  a  white,  hard 
metal.  One  part  of  brass  to  one  of  gold  gives  a  brittle  alloy. 
Tin  is  very  injurious  to  the  malleability  of  gold.  Sulphuret  of 
antimony  removes  these  metals.  Iron  does  not  so  seriously  in- 
terfere with  the  working  of  gold.  One  part  of  the  latter  metal 
combined  with  eleven  of  gold  produces  a  malleable  alloy.  Of 
the  alloys  of  gold  with  mercury  nothing  need  be  here  added  to 
what  has  already  been  said. 

Silver  unites  with  gold  in  every  proportion,  the  color  being 
nearly  proportional  to  the  amount  of  the  paler  metal  introduced. 
The  alloy  is  harder  and  more  fusible  than  gold,  the  hardest  con- 
sisting of  2  parts  of  gold  to  1  of  silver. 

*  This  metal  is  combined  with  gold  much  moi*e  generally  than  is  usually 
supposed.  Its  presence  confers  upon  the  gold  the  property  of  solubility 
in  nitre  on  fusion.  When  gold  is  purified  by  niti'e,  the  slags  are  not 
entirely  dissolved  in  water,  but  there  remains  a  fine  grayish  sediment, 
composed  of  alumina,  silica,  potassa,  oxides  of  iron,  copper,  lead,  plati- 
num, gold,  and  metallic  gold. 


314      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Copper  is  the  most  valuable  of  the  metals  for  alloying  gold, 
as  it  is  retained  with  greater  firmness,  and  communicates,  when 
properly  managed,  the  requisite  degree  of  hardness,  without  in- 
juring the  malleability  of  the  gold.  The  only  perceptible  effect 
it  has  is  to  redden  the  alloy,  a  result  which  may  be  avoided  by 
adding  silver,  or  by  treating  the  finished  work  with  caustic  am- 
monia. It  must  be  borne  in  mind,  however,  that  an  alloy  of 
gold  with  copper  about  19  carats  fine,  or,  to  speak  more  cor- 
rectly, containing  76  parts  of  gold  to  24  of  copper,  is  crystalline 
in  its  texture,  and  brittle.  This  is  a  definite  compound  and  may 
be  represented  by  the  formula  AuCu2.  The  addition  of  either 
metal  to  this  alloy  diminishes  its  brittleness. 

The  common  alloy  of  coin  is  90  gold  to  10  copper.  The  yel- 
low coin  of  the  United  States  is  composed  of  90  parts  of  gold, 
2^  of  silver,  and  1^  of  copper.  The  redder  coins  have  less  silver. 
Medals  usually  contain  more  gold,  being  less  subjected  to  abra- 
sion than  coins.  Their  proportions  are  91.6  of  gold  to  8.4  copper. 
The  common  alloy  for  jewelry  is  75  of  gold  to  25  of  copper, 
zinc  or  silver  being  occasionally  used  to  take  off  the  red  tint 
given  by  the  copper.  The  proportions  recommended  by  Dr. 
Harris  for  plate-work,  are,  for  plate  for  the  upper  jaw,  gold  20, 
copper  3,  silver  1  ;  for  plate  for  lower  jaw,  gold  21,  copper  2, 
silver  1  ;  for  springs,  gold  18,  copper  5,  silver  6. 

Some  little  care  is  needed  in  the  preparation  of  these  alloys. 
Owing  to  the  difference  in  the  specific  gravity  of  the  metals, 
they  are  liable  to  separate  from  one  another  after  fusion.  Silver, 
especially,  parts  from  gold  in  this  way.  To  obviate  this,  it  is 
necessary  to  cast  the  alloy  in  shallow  ingots,  and  should  it,  not- 
withstanding this  precaution,  be  unequally  mixed,  it  must  be 
cut  up  and  melted  over  again,  when  it  will  be  more  uniform. 
Sometimes  repeated  fusions  are  necessary  ;  generally,  however, 
two  will  suffice.  It  is  commonly  recommended  to  add  borax  to 
the  fusing  mass.  This  has  a  tendency  to  cover  the  metallic 
bath,  and  give  a  smooth  bright  surface  to  the  metal.  But  it 
is  impossible  to  secure  an  accurate  admixture  of  the  metals  with 
it,  because  it  will  infallibly  oxidate  a  portion  of  the  copper, 
and,  consequently,  insure  a  somewhat  finer  alloy  than  the 
quantities  introduced  would  make,  if  thoroughly  amalgamated. 


GOLD.  315 

This,  however,  is  a  matter  of  little  consequence  in  practical 
operations,  as  the  loss  is  trifling,  unless  excess  of  borax  is  used. 
There  is  a  peculiar  class  of  alloys,  termed  solders,  which, 
melting  at  a  lower  temperature  than  the  alloys  with  which  they 
are  used,  serve  to  unite  pieces  of  work  to  one  another.  It  is 
necessary  that  they  should  flow  smoothly  and  harden  quickly, 
in  order  that  they  may  be  worked  with  facility.  The  common 
gold  solder,  for  18  carat  gold,  is  composed  of  Q)Q.Q  parts  of  gold, 
18  carats  fine,  16.7  of  silver,  and  the  same  quantity  of  copper. 
The  following  recipes  for  solder  are  copied  from  Dr.  Harris's 
work  on  Dental  Surgery  : — 

No.  1. 
2  pennyweights  22  carat  gold. 

16  grains  fine  silver. 

12      "       rose  copper. 

No.  2. 
1  pennyweight,  15  grains,  22  carat  gold. 
16  grains  fine  silver. 
12      "       rose  copper. 

No.  3. 
6  pennyweights  pure  gold. 
2  "  rose  copper. 

1  "  fine  silver. 

The  latter  is  said  to  fuse  with  more  difficulty,  but  to  work 
better  than  the  others.  It  is,  in  fact,  16  carat  gold.  Zinc  has 
been  added  to  these  solders,  for  the  purpose  of  making  them 
melt  more  easily,  but  is  objected  to  on  account  of  the  unpleasant 
brassy  taste  communicated  by  it  to  the  mouth. 

It  will  be  seen,  by  what  has  been  just  said,  that  a  thorough 
understanding  of  the  subject  of  alloys  is  very  necessary  to  all 
workers  in  metal.  It  would  be  too  tedious,  however,  for  the 
practical  man  to  go  through  the  labor  of  analysis  and  parting, 
in  order  to  obtain  pure  materials  wherewith  to  form  his  alloys. 
The  form  in  which  the  precious  metals  are  most  commonly  used 
is  that  of  the  coins  of  various  nations.  A  table  of  these  coins 
is,  therefore,  very  necessary  to  alF  who  work  in  the  precious 
metals.  The  following  is  taken,  with  some  alteration,  from  Eck- 
feldt's  work  on  coins: — 


316      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


Table  of  Coinage  of  Different  Nations. 


Nation. 


Weight. 


Argentixe  Republic. 

Doubloon,  Province  of  Rio  de  la  Plata,         1828-32 

«  1813-32 

The  same  variations  of  fineness  and  weight  iu  coins 

of  the  same  date  are  to  be  found  in  the  silver 

coinage  of  this  republic. 


Austria. 
Ducat  of  Maria  Theresa, 
Sovereign  of  Maria  Theresa, 
Ducat  of  Leopold  II., 

"      of  Francis  I., 
Quadruple  of  Francis  I., 
Sovereign  of  Francis  I., 

"        of  Ferdinand  I., 
Half-sovereign  of  Ferdinand  I., 
Ducat  of  Ferdinand  I., 
Quadi'uple  of  Ferdinand  I., 
Hungary  ducat  of  Ferdinand  I., 


1762 
1778 
1790 
1809-34 
1830 
1831 
1838 
1839 
1838 
1840 
1839 


Baden. 
Ten  guilder  (five  guilder  same  quality)  of  Louis, 
Grand  Duke,  1819 

Bavaria. 
Ducat   of  Maximilian  Joseph   and   Charles 

Theodore,  17G4-97 

Ducat  of  Maximilian  Joseph  II.,  1800 

"      of  Louis,  1832 


Belgium. 

Forty  francs. 

Twenty  francs  in  proportion,  same  fineness, 
reigns  same  as  Austrian  coinage. 


Sove- 


Doubloon, 


Bolivia. 


1827-36 


Brazil. 
Moidore  of  Maria  I.  and  John  HI.,  1779 

Half- Joe  of  Peter  XL,  1838-38 

The  other  moidores  and  half-joes  are  of  the  same 

fineness  with  the  moidore  of  1779,  varying  slightly 

in  weight. 

Britain. 
The  gold  coins  of  this  kingdom  are  of  the  uniform 
fineness  of  915.5,  but  below  the  legal  standard 
about  one-thousandth.  The  par  value  of  the 
pound  sterling  is  about  $4  84.  Sterling  gold  is 
worth  94.6  cents  per  pennyweight. 


418 
415 


53.5 
170 

53.5 

53.7 
215.5 
174.5 
174.5 

87 

53.7 
215.5 

63.7 


105.5 


53 
53 
53.5 


199 


416.5 


125.5 
221.5 


815 
868 


985 
917 
986 
983 
983 
898 
901 
902 
985 
985 
986 


900 


980 
984 
987 


895 


870 


914 
915 


GOLD.  317 

Table  of  Coinage  of  Different  Nations — Continued. 


Brunsavick. 

X.  Thaler  of  Charles,  1745 

"  of  Charles  William  Ferdinand,  1805 
"        of  Wm.  Fred,  and  George,  Regent,  1813-19 

"         of  Charles,  1824-30 

"         of  William,  1831-38 

V.  Thaler  of  Charles,  1748-64 


Doubloons, 


Doubloons, 


Central  America. 


Chili. 


1824-33 


1819-34 
1835  and  seq. 


Colombia. 
Doubloon  of  eight  escudos,  Colombia,  Bogotan 

Mint,  1823-36 

"  "  Popayan  Mint,      1823-36 

"       of  New  Granada,  Bogata,  1837 

Half-doubloon  of  Ecuador,  Quito,  1836 

Quarter-doubloon  of  Colombia,  Bogota,         1823-36 

"  of  Ecuador,  Quito,  1835 

Eighth-doubloon  of  Colombia,  Bogota,  1823-36 

"  "         Popayan, 

These  last  coins  vary  in  fineness  from  849  to  854, 
and  in  weight  from  44^-  to  61}.  The  sixteenth- 
doubloons  are  of  the  same  quality. 


Denmark. 
Specie  ducat  of  Frederick  V., 

'<  of  Christian  VII., 

Current  ducat  of  Christian  Vll., 
Christian  d'or  of  Christian  VII., 
Double  Frederick  d'or  of  Frederick  VI. 

Egypt. 
Sequin  fundoukli  of  Achmet  III., 
"  of  Mahmoud  I., 

((  (< 

"  of  Mustapha  III., 

"  of  Abdul  Hamed, 


1749 

1795-1802 

1783 

1775 

1813-39 


1115  (1703) 
1143  (1730) 

1171  (1757) 
1187  (1773) 


ofSelimlll.,  1203(1789) 

Half-sequin  fundoukli  of  Mahmoud  II.,  1233  (1818) 
Bedidlik,  100  piastres,  of  Abdul  Majeed,  1255  (1839) 
Nusflix,  50  piasti'es,  "  " 

Kairie  Hastreen,  10  piastres,     "  " 

The  first  date  given  above  is  the  year  of  the  Hegira ; 
the  second,  the  Christian  era. 


AVeight. 

Fineness. 

Grains. 

Tbous. 

202 

898 

204 

896 

204.5 

896 

205 

896 

205 

894 

102 

903 

417 

833 

417 

867 

417 

872 

416.8 

870 

416.5 

858 

416.8 

870 

209 

844 

104 

865 

104 

844 

51 

865 

51 

852 

53.5 

988 

53.7 

979 

48 

876 

103 

905 

204.5 

895 

53 

958 

39 

940 

39 

848 

39 

781 

39 

786 

39 

645 

39 

690 

18 

670 

132.2 

874 

66.1 

875 

27 

874 

Value. 


81 

87 


91 


96 


14  96 


15  57 
15  66 


15  61  7 

15  39 

15  61  7 

7  59  6 
3  87  4 

8  78 
1  90 

1  87  1 


27  6 
26  4 
81  1 
01  4 
88  2 


2  18 
1  57 
1  42 


31 


08  3 
15  9 
51  9 
97  6 
49  1 
01  7 


318      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Coinage  of  Different  Nations — Continued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.     c.  m. 

France. 

Louis  d'or  of  Louis  XV.,                                 1726-73 

124 

897 

4   79 

of  Louis  XVL,                                1786-92 

116.5 

900 

4  51  6 

Double  Louis  d'or  of  Louis  XV.,                          1744 

250 

902 

9  71  1 

of  Louis  XVI.,                   1786-92 

235 

901 

9  11  9 

Napoleon,  20  francs,  of  Napoleon,                 1803-14 

99.2 

899 

3  84  1 

The  subsequent  gold  coinage  of  France  is  of  the 

uniform  fineness  of  899,  except  the  twenty  franc 

pieces  of  Louis  Philippe,  coined  in  1840-41,  which 

are  900. 

Greece. 

Twenty  drachms  of  Otho,                                     1833 

89 

900 

3  45 

Hanover. 

Ducat  of  George  III.,                                            1776 

53.5 

993 

2  28  8 

Pistole  or  five  thaler  of  George  III.,                    1803 

102 

896 

3  93  6 

1813-14 

102 

890 

3  91 

Ten  thaler  of  George  III.,                                1813-14 

204.5 

890 

7  83  8 

' '         WilUam  IV.  and  Ernst.  August.  1 835  &  seq. 

205 

895 

7  90  2 

Hesse. 

Ten  thaler  of  Frederick  II.,                            1773-85 

202 

890 

7  74  2 

Five  thaler  of  Frederick  II.,                            1771-84 

101 

893 

3  88  4 

of  William  IX.,                              1788-89 

101.5 

892 

3  89  9 

"          of  William  L,                                1815-17 

101.5 

894 

3  90  8 

HiNDOSTAN. 

Mohur  of  Bengal,                                                   1770 

190 

982 

8  03  5 

1787 

191 

989 

8  13  4 

««              «»                                                         1793 

191 

993 

8  16  8 

1818 

204.7 

917 

8  08  4 

'<      of  Madras,                                                    1818 

180 

917 

7  10  9 

"      of  Bombay,                                                   1818 

179 

920 

7  09  2 

Half-mohur  of  Bengal,                                            1787 

95 

984 

4  02  6 

Star  pagoda  of  Madras, 

52.5 

800 

1  80  9 

Pondicherry  pagoda  of  Pondicherry, 

52.5 

708 

1  60  1 

Porto  Novo  pagoda,  of  Portuguese  Company, 

52.5 

740 

1  67  8 

Mecklenburg  Schwerin. 

Ten  thaler  of  Frederick  Francis,                         1831 

204.5 

896 

7  89  1 

Mexico. 

Doubloon  of  Mexico,  Augustin,  Emperor,           1822 

416.5 

864 

15  49  8 

"                  "         Mexican  Republic,        1824-30 

416.5 

865 

15  51  6 

Other  doubloons  minted  at  Mexico  weigh  417  grains, 

and  are  from  867  to  869  thousandths  fine.     The 

doubloon  of  Guanaxuato  varies  from  860  to  867 

in  fineness. 

Doubloon  of  Durango, 

417 

868 

15  58  8 

H                                      11 

417 

865 

15  53  4 

1833-36 

417.5 

872 

15  67  9 

"        of  Guadalaxara, 

416 

865 

15  49  7 

GOLD.  319 

Table  of  Coinage  of  Different  Nations — Continued. 


Weight. 


Milan. 
Zecchino,  or  Sequin,  of  Maria  Theresa  and 

Joseph  II., 
Doppia,  or  Pistole,  of  Joseph  II., 
Forty  lire  of  Napoleon, 
Sovereign  of  Francis  I., 

"         of  Ferdinand  I., 
Half-sovereign, 

Naples  and  Sicily. 
Six  ducat,  of  Ferdinand  IV., 
Onzia  of  Sicily  of  Charles, 
Onzia  of  Ferdinand  I., 
Twenty  lire  of  Joachim  Napoleon, 


1770-84 
1783 

1805-14 
1831 
1838 
1839 


1788 
1751 
1818 
1813 


Netherlands. 

Ducat,  1770-1810 

"      of  William  I.,  1833-39 

Ten  guilders  of  William  I.,  1816-39 

Persia. 
Toman  of  Fatha  Ali  Shah,  Kajar,  1230-40  (1814-24) 
"      of  Mohammed  Shah,  Shakinshah,  1255  (1839) 
Half-toman  of  Mohammed  Shah,  1252  (1837) 


Poland. 
Ducat  of  Stanislaus  Augustus, 

Portugal. 
Moidore  of  Peter  II., 

It  a 

"        of  John  v., 
Half-joe, 

"        of  Maria  I.  and  Peter  III., 

"        of  Maria  I., 
of  John  VI., 
Joannese  of  John  V., 
Crown  of  Maria  II., 


1791 


1689 

1705 

1714-26 

1727-77 

1778-85 

1787-1804 

1822-24 

1730 

1838 


Prussia. 

Frederick  d'or  of  Frederick  II.,  1752-82 

of  Frederick  William  II.,        1795-9G 

"  of  Frederick  Wilhelm  III.,  1799-1812 

Double  Frederick  d'or  of  Fred.  Wilhelm  III.,  1800-11 

1831 
Ducat  of  Frederick  William  II.,  1787 


Rome. 
Sequin  of  Pius  VI., 
Doppia  of  Pius  VI., 
"      of  Pius  VII., 
Gold  scudo  of  Republic, 
Ten  scudi  of  Gregory  XVI., 


1775-83 
1777-86 

1799 
1836 


Grains. 


53.5 

97.5 

199 

174.5 

174.5 

87 


135 

68 


99 


53.5 

53.7 

103.5 


71.2 
53.7 

27 


53.5 


165 
165 
165 
217 
220 
221 
221 
439 
148 


102 
102 
102 
205 
205 
63.5 


52.5 

84 

84.5 
910 
267.5 


990 
908 
899 
898 
901 
902 


893 
85if 
995 
900 


980 
981 

899 


991 
965 
968 


984 


908 
928 
913 
914 
913 
914 
909 
912 
912 


901 

897 
901 
898 
903 
979 


996 
906 
901 
833 
900 


28  1 
81  3 
70  6 
74  8 

77  1 
38 


5  19  2 
2  51  6 

2  48  5 

3  84  8 


2  25  8 
2  26  9 
4  00  7 


3  04  2 
2  23  3 
1  12  1 


2  26  6 


6  45  2 

6  59  4 
6  48  8 
8  62 
8  65 
8  69  9 
8  65  2 
17  24  2 
5  81  3 


95  8 
94 

95  8 
92  3 
97  2 
25  6 


2  25  2 

3  27  8 
3  27  9 

:52  64  6 
10  36  8 


320      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Coinage  of  Different  Nations — Cojitinued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Russia. 

Imperial  of  Elizabeth, 

1756 

253 

915 

9  97 

Tlie  gold  coins  of  Russia,  though  irregular  in  ■weight, 

are  of  the  same  standard  fineness  dui-in 

g  the  reigns 

of  Elizabeth  and  Catharine  II. 

Ducat  of  Paul  I., 

1798 

66 

969 

2  75  4 

Three  roubles  of  Nicholas, 

1888 

60.5 

917 

2  38  9 

Half-imperial  of  Nicholas, 

1839 

100.5 

917 

8  96  9 

Sardinia. 

Pistole  of  Victor  Amadeus,  &c., 
Carlino  (island)  of  Victor  Amadeus,  &c., 

148 

905 

5  76  8 

1773 

247 

890 

9  46  7 

Marengo  of  Republic, 

1800 

98 

898 

3  79 

Eighty  lire. 

398 

898 

15  39  2 

Genovine  of  Ligurian  republic  (Genoa) 

1798 

388 

908 

15  17  2 

Saxony. 

Double  August  d'or  of  Fred.  August.  III., 

1784-1817 

204.5 

896 

7  89  1 

((                        ((                                a 

1820 

205 

898 

7  92  8 

Double  Anton  d'or  of  Anthony, 

1830-36 

205 

900 

7  94  6 

Ducat  of  Anthony, 

1830 

53.7 

979 

2  26  4 

Spain. 

Cob  doubloon  of  Philip  V.,  American, 

1733-44 

416 

895* 

10  03  4 

Doubloon  of  Ferdinand  VI.,  American, 

1751 

416 

908 

k;  26  5 

"        of  Charles  III.,  American, 

1772-84 

416 

843t 

16  00 

"        of  Charles  III.,  Spanish, 

1786-88 

416 

890 

15  58  7 

"        of  Charles  IV.  and  Ferdinand 

VII.,  i\jnerican, 

1789-1821 

416.5 

868 

15  57 

Pistole  of  Philip  V.,  Spanish, 

1745 

103 

909 

4  63  2 

"      of  Charles  III.,  American, 

1774-82 

103 

895 

3  97 

"      of  Ferdinand  VII.,  American, 

1813-24 

104 

872 

3  90  6 

Escudo  of  Charles  III.,  Spanish, 

1786-88 

52 

874 

1  95  7 

"       of  Charles  IV., 

1789-1808 

52 

808 

1  94  4 

"       of  Ferdinand  VII.,  American, 

1809-20 

52 

851 

1  90  6 

Half-doubloon  of  Charles  III.,  Spanish, 

1780-82 

206 

890 

7  95 

"            of  Charles  IV.,  American, 

1789-1808 

208 

870 

7  79  3 

"            of  Ferdinand  VII.,  Spanish,    1810-24 

208 

865 

7  74  8 

Sweden. 

Ducat  of  Gustavus  III.  and  GustavusIV., 

1777-1800 

53 

977 

2  23 

"      of  Charles  John  XIV., 

1838 

54 

975 

2  26  7 

Savitzerland. 

Pistole  of  Berne, 

1796 

116 

901 

4  50  1 

"      of  Basle, 

1795 

118 

891 

4  52  8 

"      of  Soleure, 

1798 

116 

898 

4  48  6 

"      of  Helvetian  Republic, 

1800 

116 

897 

4  48  1 

Ducat  of  Berne, 

1794 

52.5 

974 

2  20  2 

"      of  Basle, 

53 

943 

2  15  2 

*  Varies  from  803  to  I 


,  t  Varies  from  8S3  to  S93,  the  oldest  pieces  being  the  best. 


GOLD. 


321 


Table  of  Coinage  of  Different  Nations — Continued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Tlious. 

(1.     c.  m. 

Tunis. 

Half-sequin  of  Abdul  Hamed, 

1773 

19 

885 

72  4 

Turkey. 

Sequin  fondouk  of  Selim  III., 

1789 

52.5 

800 

1  80  9 

"      zermaliboub  of  Selim  III., 

1789 

36 

800 

1  24 

Ohikilik  of  jVIahmoud  II., 

1822-24 

25 

833 

89  7 

Twenty  piastres  of  Mahmoud  II., 

1827 

27.5 

875 

1  03  7 

Yirmilik,  20  piastres,  of  Abdul  Medjid, 

1840 

24.5 

832 

87  7 

Tuscany. 

Ruspone  of  Francis  III.  to  Leopold  III., 

1738-1800 

160 

997 

6  87 

"        of  Louis  I.  and  Charles  I., 

1801-07 

161 

998 

6  91  9 

"        of  Leopold  II., 

1824-34 

161 

999 

6  92  5 

Sequin  of  Leopold, 

1765-79 

53 

997 

2  27  6 

"      of  Leopold  II., 

1824-34 

53.5 

999 

2  30  1 

United  .States. 

Eagle, 

1792-1834 

270 

916.7 

10  67  4 

" 

1834-1837 

258 

899.2 

9  99  7 

le 

37  and  seq. 

258 

900 

10 

WURTEMBERG. 

Ducat  of  Charles, 

1790-1818 

53 

980 

2  23  7 

Articles  of  jewellery  were  formerly  rarely  to  be  found  in  the 
melting  pots  of  the  goldsmith,  but  fashion  now  changes  their 
form  almost  as  rapidly  as  it  does  that  of  less  costly  toys.  They 
are  extremely  irregular  in  their  composition.  As  a  general 
thing,  however,  the  percentage  of  fine  gold  contained  in  them 
is  small.  It  may  be  said  to  average  in  American  jewellery  from 
12  to  14  carats.  Often,  in  bulky  articles,  the  core  or  basis  of 
the  jewel  is  made  of  some  cheap  alloy,  which  is  covered  so 
thickly  with  the  gold  that  it  can  hardly  be  said  to  be  plated. 
The  British  standard  for  jewellery  is  22  to  18  carats ;  the  French, 
22i'g,  22^,  and  18  ;  the  Austrian,  IB/^  and  13 J^ ;  the  Mexi- 
can, 20.     These  qualities  are  usually  stamped. 

Jewellery  is  subject  to  a  very  great  loss  in  melting,  which  varies 
with  the  kind  subjected  to  the  action  of  the  fire.  Part  of  this 
is  owing  to  the  dirt  which  accumulates  in  the  numerous  cavities, 
part  to  the  quantity  of  solder  used  in  the  construction  of  the 
pieces.  This  sort  of  bullion  is  always  refined  with  nitre. 
21 


322       CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


SALTS    OF   GOLD. 

The  salts  of  gold  are  few  and  imperfectly  known.  The  sul- 
pho-salts  are  usually  combinations  of  some  sulphacid  with  the 
sesquisulphuret  of  this  metal.  Thus  the  sulpharseniate  of  gold 
is  composed  according  to  the  formula  2AU2S3,  3AS2S3. 

Oxide  of  gold  also  enters  into  triple  combinations  with  some 
of  the  oxacids  and  another  base.  Thus,  hyposulphite  of  po- 
tassa  or  soda  attacks  the  oxide  of  gold  and  forms  with  it  durable 
salts,  dithionites  of  the  alkaline  base  and  of  protoxide  of  gold.  If 
terchloride  of  gold  be  added,  in  successive  portions,  to  hyposul- 
phite of  soda  until  the  yellow  color  disappears,  and  the  solution 
then  be  evaporated  to  the  point  of  crystallization,  the  greater 
part  of  the  hyposulphite  and  sulphate  of  soda  separates.  The 
liquid  again  crystallized  yields,  among  others,  colorless  needles, 
which,  by  solution  in  alcohol  of  0.9  and  spontaneous  evaporation, 
furnish  the  same  crystals.  They  are  probably  dithionite  of  soda 
and  gold. 

The  haloid  salts,  however,  are  the  most  numerous  and  best 
understood.  They  are  yellow  or  orange  color  ;  let  fall  the  pur- 
ple of  Cassius  with  the  salt  of  tin  when  very  dilute,  and  metallic 
gold  as  a  brown  impalpable  powder  with  protosulphate  of  iron, 
and  other  deoxidating  reagents. 

Chlorides. — 1.  The lyrotochloride  of  gold,  AuCl  (234.62),  is 
formed  by  evaporating  the  terchloride  and  heating  it  in  a  porce- 
lain basin  to  about  450°,  with  constant  stirring  until  chlorine  is 
no  longer  given  off.  At  a  higher  heat,  but  below  redness,  it  is 
completely  decomposed,  all  the  chlorine  being  dispelled,  and 
metallic  gold  left.  Hot  water  completely  decomposes  it,  re- 
solving it  into  terchloride  and  metallic  gold,  and  potassa  converts 
it  into  protoxide  of  gold,  chloride  of  potassium  remaining  in 
solution. 

2.  Terchloride  of  Gold,  AuClj.  305.46.— This  is  the  form 
in  which  gold  is  usually  obtained  in  solution,  and  the  salt  which 
is  applied  to  the  greatest  number  of  practical  purposes  in  the 
arts.  The  method  of  obtaining  it  has  already  been  described. 
"When  the  entire  solution  of  the  gold  is  not  an  object,  the  ex- 


GOLD.  323 

pulsion  of  nitric  acid  is  most  conveniently  effected  by  using  an 
excess  of  metal.  When  crystals  are  to  be  made,  the  solution 
thus  obtained  is  to  be  evaporated  on  a  water-bath,  at  a  very 
gentle  heat ;  when  the  concentration  is  sufficient,  the  solution  is 
removed,  and  crystallizes  immediately  on  cooling.  As  the  salt 
is  highly  deliquescent,  it  must  be  bottled  at  once  in  well-closed 
and  warmed  phials.  The  crystals  must  be  dried  rapidly,  but 
without  any  increase  of  heat,  as  it  is  fusible  at  a  very  low 
temperature,  and  decomposed  at  300°.  The  crystals  are  acicu- 
lar,  and  of  a  brilliant  ruby-red  color. 

The  solution  is  yellow  when  dilute,  deep  orange-red  when 
concentrated.  It  is  reduced  in  part  in  a  closed  glass  vessel, 
on  one  side  of  which  metallic  gold  is  deposited.  It  is  reduced 
by  phosphorus,  hydrogen,  phosphuretted  hydrogen,  sulphurous 
acid,  and  the  sulphites,  nitric  oxide,  peroxide  of  nitrogen,  and 
nitrite  of  potassa  in  the  cold,  and  by  sulphur  and  selenium 
with  the  aid  of  heat.  It  is  reduced  by  most  of  the  metals, 
by  arscniuretted  andantimoniuretted  hydrogen,  terchloride  of  an- 
timony and  white  arsenic,  and  protosalts  of  iron.  Protochloride  of 
tin  precipitates  brown  gold-tin  from  a  strong,  and  purple  of  Cassius 
form  a  weak  solution.  Protonitrate  of  mercury  gives  a  dark 
blue  precipitate.  It  is  also  reduced  by  most  organic  bodies, 
whether  in  solution  or  not,  especially  by  the  addition  of  potassa. 
Oxalic  acid  and  oxalate  of  ammonia  precipitate  gold  in  very  thin 
leaves.  Potassa,  soda,  strontia,  lime,  magnesia,  and  oxide  of 
zinc  throw  down  the  greater  part  of  the  gold  as  an  impure  ox- 
ide or  a  basic  salt,  the  precipitate  by  the  last  two  being  easily 
purified  by  nitric  acid.  Sulphuretted  hydrogen  throws  down 
sulphuret  of  gold  soluble  in  alkaline  sulphurets.  Ammonia  pre- 
cipitates a  bright  yellow  substance,  which  is  a  basic  salt  mixed 
with  fulminating  gold. 

Chlor auricles. — The  terchloride  of  gold  combines  directly  with 
nearly  all  the  metallic  protochlorides,  forming  compounds  which 
contain  3  equivalents  of  chlorine  in  the  chloracid  to  1  in  the 
chlorobase.  They  are  almost  all  orange-colored  in  the  crystal- 
lized state,  becoming  paler  yellow  by  efflorescence,  but  deep  red 
when  anhydrous.  The  chlorauride  of  potassium  will  serve  as  the 
type  of  these  compound  salts.     The  anhydrous  salt  is  composed 


324  CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST 

according  to  the  formula  KCl,  AUCI3,  and  contains  52.4  per 
cent,  of  gold.  The  crystals  are  expressed  by  KCl,  AuClg^- 
5H0,  and  contain  46.84  per  cent,  of  metallic  gold.  These  crys- 
tals are  rhombic  prisms  or  six-sided  tables,  efflorescent,  losing 
water  at  212°,  without  farther  decomposition,  soluble  both  in 
■water  and  alcohol.  At  a  higher  heat  than  the  boiling  point  of 
water,  they  are  converted  into  double  protochlorides. 

Bromides. — The  terhromide  of  gold,  formed  by  dissolving  the 
metal  in  nitrohydrobromic  acid,  is  obtained  by  evaporation  as  a 
red  mass,  which  combines  with  metallic  bromides  to  form  brom- 
aurides,  in  the  same  manner  as  the  terchloride  forms  chlorau- 
rides.  These  salts  are  hydrated  and  purple  or  brownish-red  in 
tint. 

Iodides. — Protiodide  of  gold,  Aul.  325.5. — This  salt  is 
formed  in  several  ways.  It  may  be  obtained  by  the  action  of 
hydriodic  acid  upon  oxide  of  gold,  or  the  finely  divided  metal,  in 
which  latter  case  it  must  be  aided  by  nitric  acid  ;  or,  lastly,  by 
double  decomposition,  the  terchloride  being  treated  with  iodide 
of  potassium.  The  latter  agent  must  be  added  gradually  to  a 
solution  of  the  terchloride  till  it  ceases  to  produce  a  precipitate. 
A  jellowish  crystalline  powder  falls,  which  is  to  be  washed  first 
with  alcohol  and  then  with  water.  This  substance  is  decom- 
posed by  acids  only  when  heated,  readily  by  alkalies,  by  hydriodic 
acid,  iodide  of  potassium  and  of  iron. 

Teriodide  of  Gold,  Aulg.  578.1. — This  salt  is  prepared  by 
adding  gradually  terchloride  of  gold  to  a  dilute  solution  of  iodide 
of  potassium,  till  it  becomes  dark-green.  The  liquid  is  then 
agitated  till  the  precipitate  is  redissolved,  and  more  terchloride 
added,  which  precipitates  the  teriodide.  It  is  dark-green,  easily 
decomposed,  soluble  in  hydriodic  acid,  forming  a  dark-brown 
crystallizable  solution,  and  unites  with  basic  iodides  to  form 
iodaurides,  analogous  to  the  chloraurides  and  bromaurides  already 
adverted  to. 


SILVER.  325 


CHAPTER    III. 

SILVER. 

This  is  also  a  long-known  metal.  The  most  ancient  of  books, 
Job,  speaks  of  it,  and  we  are  told  that  Abraham  was  rich  in 
silver  and  gold.  It  is  not  so  universally  found  native  as  gold, 
and  requires  more  art  to  extract  it  from  its  ores;  yet  its  greater 
abundance  gives  it  a  lower  relative,  and  its  inferior  resistance 
to  oxidating  and  corroding  agents  a  less  positive  value  than  the 
last  described  metal.  The  mediaeval  writers  called  it  a  perfect 
metal,  because  it  could  be  revived  from  its  oxide  by  the  simple 
application  of  heat,  and  because  it  could  resist  the  fiery  experi- 
mentum  crucis  which,  to  their  imperfect  apprehensions,  seemed 
to  destroy  the  baser  metals.  Its  correlative  planet,  in  that 
singular  astro-chemical  system,  was  the  moon,  as  that  of  gold 
was  the  sun.  This  old  nomenclature  is  still  retained,  to  a  cer- 
tain extent,  in  the  common  language  of  the  apothecary.  Fused 
nitrate  of  silver  is  still  called  lunar  caustic,  and  the  arborescent 
form  of  the  precipitated  metal  bears  its  ancient  name,  Arhor 
Dianse. 

Silver  is  found  native  in  most  of  the  mines  in  which  this  metal 
is  worked.  Its  crystals  are  octohedral,  or  cubic,  or  have  forms 
derived  from  these.  Sometimes  it  is  found  dendritic,  the 
arborescence  being  composed  of  minute  crystals  connected 
together.  Again,  it  occurs  in  filaments,  perforating  the  vein 
stone  in  all  directions,  and  in  sheets  coating  the  surface  of  the 
rocks  or  filling  up  its  seams.  At  the  Lake  Superior  copper 
mines,  it  is  found  in  the  native  copper  in  small  cavities,  called  by 
the  workmen  pockets  or  purses.  Large  masses  of  it,  some  of 
them  weighing  many  hundred  pounds,  have  also  been  met  with. 
The  metals  most  commonly  alloying  the  native  silver  are  gold, 
arsenic,  copper,  and  iron.  The  usual  form  in  which  this  metal 
is  obtained  is  a  sulphuret,  combined  with  lead,  copper,  anti- 
mony, or  iron.     It  is  more  frequently  mixed  with  lead  than  with 


326      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

any  other  metal.  But  little  galena  can  be  found  which  does  not 
contain  a  trace  at  least  of  silver.  Chloride  of  silver,  or  horn 
silver,  is  occasionally  met  with.  The  carbonate  is  rare  as  a 
native  product. 

METALLURGIC  TREATMENT  OF  SILVER  ORES. 

The  treatment  of  the  ores  of  silver  varies  with  the  nature  of 
the  ore  itself.  There  are  two  prominent  modes  of  working 
them — smelting  and  amalgamation.  The  former  method  is  used 
for  the  richer,  the  latter  for  the  poorer  ores.  Argentiferous 
galena  is  first  smelted  to  obtain  silver-lead,  and  then  either 
crystallized  or  cupelled  to  separate  the  more  valuable  metal. 
The  process  of  amalgamation  varies  in  different  places.  The 
method  of  Mexico  and  that  of  Saxony  are  the  two  prominent 
ones,  and  a  brief  sketch  of  them  will  suffice  to  give  a  general 
view  of  the  process. 

AMALGAMATION. 

Mexican  MetJiod. — The  ore  is  prepared  for  amalgamation  by 
stamping  it  finely  in  a  mill,  and  then  reducing  this  stamped  ore 
to  a  thin  mud,  by  crushing  it  with  heavy  rollers  or  crushers 
under  water.  The  more  minute  and  thorough  this  division  of 
the  ore,  the  more  completely  will  the  quicksilver  unite  with  the 
metal.  This  metalliferous  mud  is  transferred  to  the  jja^zo,  or 
amalgamation  floor,  and  there  mixed  with  saltierra,  a  coarse 
impure  salt,  and  thoroughly  incorporated  by  shovelling  the  heaps 
over  and  over,  and  trampling  them  with  horses'  hoofs.  A  magis- 
tral, obtained  by  roasting  copper  pyrites,  is  then  stirred  in  and 
very  completely  mixed,  as  before,  by  trampling.  Lime  is  some- 
times added.  The  materials  now  being  all  prepared,  the  mer- 
cury is  introduced  by  sifting  it  through  a  coarse  canvas  bag. 
The  mass  is  now  trodden  again  by  horses,  and  turned  over  with 
shovels  until  the  amalgamation  of  the  first  quantity  of  mercury 
is  found  to  be  complete,  a  state  of  things  determined  by  a  simple 
washing  assay.  More  mercury  is  then  added,  and  when  it  has 
taken  up  all  the  silver  it  can,  another  portion  is  added,  and  so 
on  till  the  silver  is  exhausted.     The  amalgamated  ore  is  now 


SILVEK.  327 

transferred  to  vats  of  water,  in  which  horizontal  beams,  set  with 
long  wooden  teeth,  are  made  to  turn  with  great  rapidity.  The 
water  is  thus  briskly  agitated,  and  this  motion  insures,  after  a 
time,  the  perfect  separation  of  the  lighter  earthy  matters  from 
the  heavy  metallic  amalgam.  The  latter  settles  to  the  bottom, 
and  is  afterwards  collected  and  subjected  to  heat  in  a  distilling 
apparatus,  which  drives  oif  the  mercury  and  leaves  the  porous 
silver  behind.  This  is  cast  into  bars  of  about  1,080  ounces  each. 
The  loss  of  silver  is  about  five  ounces  to  each  bar,  that  of  mer- 
cury, from  2|  upon  the  finer  ores  to  9  upon  the  coarse. 

The  chemical  changes  effected  in  the  ore  by  this  process  may 
be  thus  explained.  The  magistral,  or  combined  sulphate  of 
iron  and  copper,  being  mixed  with  the  salt,  a  double  decomposi- 
tion ensues,  the  chlorides  of  iron  and  copper  being  formed  on 
the  one  hand  and  sulphate  of  soda  on  the  other.  The  deuto- 
chloride  of  copper  reacts  upon  the  silver,  converting  it  into 
chloride  of  silver,  and  becoming  itself  protochloride  of  copper. 
The  mercury,  in  presence  of  the  saline  menstruum,  reduces  the 
chloride  of  silver,  and  the  remaining  quicksilver  amalgamates 
with  the  silver.  The  chloride  of  mercury  thus  formed  is  par- 
tially decomposed  by  the  sulphate  of  silver  resulting  from  the 
direct  reaction  of  the  sulphates  on  the  silver.  Quicklime 
counteracts  the  injurious  effect  of  too  much  magistral,  by  decom- 
posing the  resulting  sulphate. 

Saxon  Method. — The  ores  for  amalgamation  by  this  process 
are  carefully  selected,  and  so  mixed  that  their  average  yield  shall 
be  from  3f  to  4  ounces  in  the  100  pounds.  All  those  which  con- 
tain more  than  7  per  cent,  of  lead,  or  1  per  cent,  of  copper,  are 
rejected,  because  the  lead  would  render  the  amalgam  very  impure 
and  the  copper  would  be  wasted.  It  is  necessary  that  the  ores 
contain  a  certain  proportion  of  sulphur,  that  they  may  decom- 
pose enough  salts,  during  the  process  of  roasting,  to  disengage 
chlorine  sufficient  to  convert  all  the  silver  present  into  a  chloride. 
The  ores,  having  been  selected  and  mixed  in  due  proportion,  are 
now  incorporated  with  10  per  cent,  of  their  weight  of  common 
salt.  The  salted  ore  is  then  roasted,  with  frequent  stirring,  at 
first  at  a  low  temperature,  just  heat  enough  being  applied  to 
keep  the  mass  at  dull  redness,  and  then,  when  the  conversion  of 


328      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

the  sulphur  into  sulphuric  acid  is  complete,  at  a  higher  tempera- 
ture, sufficient  to  decompose  the  sulphates,  converting  them  into 
chlorides  with  the  simultaneous  formation  of  sulphate  of  soda. 
The  ore  having  heen  brought  into  this  condition,  is  now  ground 
and  bolted  to  an  impalpable  powder. 

The  finely  comminuted  ore  is  introduced  into  casks  con- 
taining 3  cwt.  of  water  to  every  10  cwt.  of  ore.  Into  this 
mixture  are  thrown  scraps  of  iron,  which  are  renewed  as  fast  as 
they  are  dissolved.  These  decompose  the  metallic  chlorides, 
throwing  down  metallic  copper  and  silver  in  a  finely  divided 
state.  The  casks  are  now  set  to  revolve  hoiizontally,  till  the 
ore  and  water  are  reduced  to  a  uniform  pap,  which  must  not  be 
too  thin,  or  the  mercury  will  sink  to  the  bottom ;  nor  too  thick, 
or  it  will  float  on  the  surface.  The  mercury  is  now  introduced, 
one-half  the  weight  of  the  ore,  and  the  barrels  are  made  to 
revolve  22  times  in  the  minute.  This  combines  the  metals  with 
the  quicksilver  in  a  complex  amalgam.  During  this  change,  the 
temperature  rises  so  that,  even  in  winter,  it  sometimes  stands 
so  high  as  104°  Fahrenheit. 

The  amalgamation  being  completed,  the  casks  are  filled  with 
water  and  revolved  slowly  till  the  amalgam  collects  at  the  bot- 
tom. This  is  drawn  off,  and  is  found  to  have  exhausted  the 
silver  very  completely,  the  metal  remaining  in  the  ore  amounting 
to  not  more  than  .15  to  .18  of  an  ounce  per  cwt.  The  quantity  of 
mercury  used  amounts  to  .95  of  an  ounce  for  every  pound  of  silver 
obtained.  The  amalgam  is  now  poured  into  wet  canvas  bags 
and  pressed,  to  get  rid  of  uncombined  quicksilver,  and  then 
placed  in  a  peculiar  distilling  apparatus,  when  the  mercury  is 
volatilized  and  a  porous  mass  of  metal  remains  behind,  which 
contains  the  silver  mixed  with  copper,  lead,  bismuth,  nickel, 
antimony,  cobalt,  zinc,  arsenic,  and  iron.  This  is  refined  by 
cupellation.  The  silver  remaining  in  the  casks  is  submitted  to 
a  fresh  amalgamation. 

SMELTING. 

This  process  presents  nothing  peculiar.  It  is  only  the  com- 
paratively rich  ores  that  can  be  worked  in  this  way,  and  very 


SILVER.  329 

large  losses  have  been  sustained  by  attempting  to  smelt  ores 
which  were  not  adapted  to  this  method  of  working.  The  ores 
best  suited  to  it  are  those  which  are  composed  of  the  mixed 
sulphurets  of  lead,  or  copper  and  silver.  These  are  smelted 
with  the  addition  of  iron,  by  means  of  which  a  lead  is  obtained 
rich  in  silver,  and  a  slag  containing  lead,  copper,  and  silver. 
This  lead-stone,  as  it  is  called,  is  roasted  and  smelted  again.  A 
similar  division  into  a  silver-lead  and  a  lead-stone  takes  place, 
and  the  roastinof  and  smeltino-  are  continued  as  lonf;;  as  the 
quantity  of  metal  obtained  pays  for  the  labor  and  materials 
used  to  separate  it. 

METALLURGIC    TREATMENT    OF    THE    ALLOYS    OF    SILVER. 

The  management  of  alloys  of  silver  differs  with  the  nature  of 
the  alloy  and  the  amount  to  be  operated  upon.  In  the  small 
way,  alloys  may  be  treated  either  by  the  dry  or  the  humid 
method,  but  on  the  large  scale,  the  dry  process  alone  can  be 
employed.  The  first-named  processes  will  be  first  described, 
and  then  the  modifications  of  them  which  are  necessary  in  order 
to  work  successfully  on  the  great  scale. 

When  the  mixed  metals  are  contaminated  with  much  earthy 
matter,  as  the  sweepings  of  a  silversmith's  shop,  the  fragments 
of  old  crucibles  which  have  been  used  for  melting  silver,  &c.,  it 
is  necessary  first  to  get  rid  of  these  earthy  matters  by  fusion 
with  carbonate  of  soda  or  borax.  Black  flux,  which  is  an  in- 
timate mixture  of  charcoal  and  carbonate  of  potassa,  has  been 
used  for  the  same  purpose.  Nitre  is  advantageously  combined 
with  these  fluxes,  as  it  oxidates  the  baser  metals  at  the  same 
time  that  it  assists  to  flux  the  earths.  Litharge  is  also  used  for 
this  purpose,  as  well  as  for  the  oxidation  of  sulphurets  and  the 
more  oxidizable  metals. 

SCORIFICATION. 

This  process  is  commonly  used  in  the  assay  of  silver  ores, 
especially  the  sulphurets,  but  is  also  applicable  to  the  reduction 
of  alloys,  more  particularly  that  of  tin  and  silver,  two  metals 
very  diflScult  to  separate  in  the  dry  way. 


330      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

This  operation  is  performed  in  deep  saucers  of  refractory 
earths  called  scorifiers,  which  are  heated  in  the  muffle  of  a 
cupelling  furnace.  The  ore  or  alloy  is  reduced  to  a  state  of 
minute  division,  mixed  with  granulated  lead  and  borax,  and 
introduced  into  the  scorifiers.  Lead  may  be  used  alone,  but  the 
addition  of  borax  facilitates  the  operation  and  protects  the  scori- 
fiers. A  gradual  heat  having  been  first  applied,  the  door  is 
closed,  and  the  fire  pushed  to  fuse  the  materials,  and  then,  the 
door  being  opened  again,  a  current  of  air  is  admitted,  and  the 
roasting  or  oxidation  begins.  Fumes,  of  colors  varying  with  the 
character  of  the  burning  substances,  are  now  given  off",  a  move- 
ment is  observed  upon  the  surface  of  the  bath,  the  scoriae  are 
thrown  to  the  sides,  forming  a  ring,  in  the  centre  of  which  is 
the  fused  metal,  constantly  diminishing  in  size  as  the  oxidation 
advances.  The  borax  dissolves  the  oxides  as  fast  as  they  are 
formed,  and  keeps  the  slag  perfectly  fluid  during  the  entire 
operation.  There  is  obtained,  as  the  result  of  this  process,  an 
alloy  of  lead  and  silver,  which  is  to  be  cupelled. 

The  proportion  of  lead  and  borax  varies.  For  alloys  con- 
taining zinc  or  tin,  much  of  the  latter  reagent  must  be  used. 
For  the  tin  alloy,  16  parts  of  oxide  of  lead  and  3  of  borax  are 
the  best  proportions. 

CUPELLATION. 

This  is  a  very  ancient  process  for  the  separation  of  the  pre- 
cious metals  from  their  alloys.  It  depends  for  its  success  upon 
the  property  of  certain  oxides  to  soak  or  filter  through  the  pores 
of  the  cupel,  while  the  fused  metals  remain  upon  its  surface. 
Much  depends  on  the  skill  of  the  workman,  much  on  the  struc- 
ture of  the  cupel.  The  latter  should  be  sufficiently  loose  in 
texture  to  enable  the  fused  oxides  to  pass  through  with  ease, 
and  yet  solid  enough  to  bear  the  necessary  handling.  It  should 
also  be  made  of  a  substance  which  is  infusible  in  the  oxides  of 
lead  or  bismuth,  as  these  are  the  only  substances  used  in  this 
operation,  they  alone  possessing  the  property  of  passing  through 
the  cupel  and  of  carrying  other  oxides  with  them. 

This  operation  is  conducted  in  a  muffle.      The  furnace  is 


SILVER.  331 

heated,  the  cupels  introduced  and  kept  empty  till  the  inside  of 
the  muffle  is  reddish-white.  Care  having  been  taken  to  remove 
all  foreign  matters  which  may  have  fallen  into  the  cupels,  the 
substances  to  be  experimented  on  are  now  put  in.  If  they  are 
alloys  which  contain  the  necessary  amount  of  lead  to  carry  off 
all  the  oxides  through  the  pores  of  the  cupel,  they  are  directly 
introduced ;  if  not,  they  are  first  wrapped  in  a  sheet  of  lead  of 
the  necessary  weight,  or  fused  with  litharge,  or  laid  carefully 
on  a  bath  of  metallic  lead  previously  fused  in  the  cupel.  When 
they  are  in  small  grains,  it  is  well  to  wrap  them  in  a  very  thin 
sheet  of  lead  and  drop  them  into  the  metallic  bath. 

The  muffle  is  now  closed,  either  by  the  door  or  by  pieces  of 
charcoal,  till  the  alloys  have  been  brought  to  the  same  temper- 
ature with  the  muffle.  When  this  point  has  been  attained,  air 
is  admitted.  The  metal,  which  has  been  very  smooth  with  a 
convex  surface,  becomes  very  lustrous  as  soon  as  the  air  touches 
it.  Bright  iridescent  patches  make  their  appearance.  Glancing 
lights  flash  over  the  surface,  and  pass  off  to  the  sides  in  rain- 
bow-colored rings.  This  is  due  to  the  formation  of  the  oxide  of 
lead,  which,  being  absorbed  by  the  cupel  as  fast  as  it  is  formed, 
is  perpetually  covering  and  uncovering  the  metallic  bath,  and 
giving  rise  to  the  motion  from  the  centre  to  the  circumference. 
At  the  same  time  a  lead-vapor  rises  and  fills  the  muffle,  and 
there  is  formed  round  the  metal  a  ring,  which  continually  in- 
creases till  it  reaches  the  edge.  The  metallic  bath  regularly 
diminishes  during  the  progress  of  this  operation,  the  shining 
points  on  its  surface  become  larger  and  move  more  rapidly ;  at 
last  the  button  is  agitated  by  a  rapid  movement,  which  causes  it 
to  turn  round  on  its  axis.  Then  it  remains  quiet,  and,  though 
dull  at  first,  soon  assumes  the  appearance  of  pure  silver.  This 
last  stage  has  been  termed  the  brightening,  fulgwation,  or 
coruscation. 

The  cupel  must  be  gradually  cooled,  or  the  assay  will  vegetate; 
that  is,  it  will  be  covered  with  small  protuberances  over  its  sur- 
face, and  it  may  even  spirt  out  and  cause  a  loss  of  silver.  This 
has  been  attributed  to  the  sudden  contraction  of  the  surface  of 
the  metal,  produced  by  rapid  cooling,  while  the  centre  of  the 
mass  is  still  fluid.     It  may,  in  part,  be  due  to  this  cause,  but 


332      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

more  probably  to  the  escape  of  absorbed  oxygen,  as  will  be 
hereafter  explained. 

The  proper  management  of  the  temperature  is  a  matter  of 
great  importance  to  the  success  and  economy  of  this  method  of 
reducing  silver.  If  the  heat  be  too  high,  some  silver  will  be 
volatilized;  if  too  low,  the  same  thing  will  take  place  on  account 
of  the  length  of  time  necessary  to  complete  the  reduction.  The 
suitable  degree  of  heat  is  ascertained  by  the  bright  redness  of 
the  cupel,  and  the  clear,  luminous  appearance  of  the  melted 
metal.  If  the  cupels  are  white,  the  metal  scarcely  visible,  the 
fumes  indistinct  and  rising  rapidly  to  the  arch  of  the  muffle,  the 
furnace  is  too  hot.  If,  on  the  other  hand,  the  smoke  is  thick 
and  heavy,  and  falls  in  the  muffle,  and  if  the  litharge  forms 
lumps  and  scales  about  the  metal,  it  is  not  hot  enough.  It  is 
best  to  give  a  strong  heat  at  first,  then  to  cool  dowm  a  little,  and, 
towards  the  end  of  the  process,  to  increase  the  temperature 
again.  The  operation  is  usually  more  successful  at  too  high 
than  at  too  low  a  heat. 

The  force  of  the  current  of  air  which  passes  through  the 
muffle  is  also  a  very  important  circumstance.  Too  strong  a 
current  cools  the  cupel,  and  oxidates  the  lead  too  rapidly;  too 
feeble  a  one  renders  the  operation  so  slow  that  much  silver  is 
volatilized.  If  the  operation  has  been  successful,  the  button 
will  be  well  rounded,  white,  crystalline  below,  and  easily  detached 
from  the  cupel. 

Cupellation,  however  carefully  conducted,  never  separates 
from  the  alloy  the  entire  amount  of  silver.  There  is  always 
some  of  the  precious  metal  lost  by  volatilization,  a  notable  pro- 
portion of  it  being  found  in  the  dust  or  soot  deposited  by  the 
lead  vapors  already  described  as  filling  the  muffle  during  the 
operation.  Silver  is  also  lost  by  oxidation,  in  which  case  it 
penetrates  the  cupel,  and  there  is  a  farther  loss  arising  from  the 
tendency  of  the  silver-lead  to  pass  into  the  cupel.  The  total 
amount  of  loss  for  alloys  rich  in  silver  has  been  estimated  at 
.0003,  or  .03  per  cent.,  and  for  the  poorer  alloys  at  .002,  or  2 
per  cent. 

In  selecting  a  cupel,  there  is  no  difficulty,  if  the  necessary 


SILVER.  333 

amount  of  lead  be  known,  for  these  little  Instruments  absorb 
their  own  weight  of  litharge. 

The  metals  contained  in  the  alloy  are  indicated  by  the  appear- 
ance of  the  cupels  after  the  operation  has  been  concluded. 
Pure  lead  colors  the  cupel  straw-yellow  verging  on  lemon-yellow; 
bismuth,  straw  color  passing  into  orange  ;  copper,  a  gray,  dirty 
red  or  brown  ;  iron  produces  black  scorise,  found  at  the  circum- 
ference of  the  cupel ;  tin  forms  a  gray  slag.  Zinc  leaves  a 
yellowish  ring  on  the  cupel,  becoming  white  as  it  cools.  Anti- 
mony and  sulphate  of  lead  produce  yellow  scoriae  which  crack 
the  cupel. 

The  modifications  of  this  process  for  reducing  silver  on  the 
large  scale  are  confined  entirely  to  matters  of  detail.  The 
cupel  is  made  upon  the  base  of  a  large  furnace  hearth,  which 
usually  contains  several  layers ;  first,  the  masonry  of  the  founda- 
tion, then,  a  bed  of  hard  rammed  scoriaj,  and,  lastly,  bricks  set 
on  end,  forming  the  permanent  area  of  the  furnace.  Leached 
wood  ashes  from  the  soap  factories  constitute  the  material  for 
these  great  cupels.  They  are  sometimes  mixed  with  lime,  clay, 
marl,  or  bone-ash.  They  are  well  beaten  in  over  the  upper  layer 
of  the  hearth.  When  the  cupel  is  formed,  it  is  a  basin-shaped 
cavity,  containing,  in  some  works,  a  smaller  cavity  in  the  centre 
for  the  reception  of  the  silver,  and  a  gutter  at  the  side  to  run 
ofi"  the  litharge.  In  the  Hartz  Mountains,  the  furnaces  have  a 
movable  iron  dome  which  may  be  let  down  upon  them  during 
the  operation,  and  one  or  more  pair  of  bellows  fixed  in  the  side 
walls.  The  silver-lead  is  laid  upon  the  hearth,  and  as  soon  as 
the  ebullition  of  the  melted  metal  has  ceased,  the  bellows  begin 
to  play  over  the  surface  at  the  rate  of  four  or  five  blasts  to  the 
minute.  This  oxidates  the  lead,  and  the  heat  being  now  urged, 
a  grayish  froth,  composed  of  oxidized  metals  and  impurities, 
makes  its  appearance.  This  is  raked  ofi",  and  then  the  clear 
litharge  begins  to  form.  This  is  also  drawn  ofi",  the  gutter  being 
deepened  as  the  level  of  the  liquid  falls.  Towards  the  close  of 
the  process,  the  litharge  becomes  rich  in  silver,  and  is,  therefore, 
laid  aside  separately  from  that  which  was  first  formed.  The 
colored  particles  of  oxide  of  lead  now  move  with  great  rapidity 
over  the  surface;  the  alloy  is  less  fusible,  and  the  silver-cake  is 


334      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

soon  perfectly  formed.  As  soon  as  fulguration,  or  the  total 
disappearance  of  the  oxide  of  lead,  takes  place,  the  fire  is 
checked,  the  bellows  stopped,  and  a  stream  of  hot  water  thrown 
upon  the  silver-cake.  This  is  refined  by  a  new  cupellation  in  a 
more  carefully  made  cupel. 

The  litharge  of  the  cupel  is  now  smelted  to  obtain  metallic 
lead.  The  total  loss  of  lead  is  estimated  at  4  per  cent.  In  the 
Frankensham  works,  much  of  this  loss  is  obviated  by  conducting 
the  smoke  through  long  flues  in  which  the  lead  fumes  are  con- 
densed into  a  metallic  soot. 

In  connection  with  this  subject,  it  is  proper  to  state  an  attri- 
bute of  silver,  discovered  by  MM.  Lucas  and  Gay  Lussac.  They 
have  proved  that  metallic  silver,  when  fused  in  the  air,  absorbs 
oxygen  and  gives  it  out  again  in  the  act  of  solidification.  The 
quantity  thus  absorbed  may  amount  to  twenty-two  times  the 
volume  of  the  silver. 

The  phenomena  presented  by  a  large  mass  of  the  metal  under- 
going this  process,  are  very  peculiar.  The  consolidation  com- 
mences at  the  edges  and  advances  towards  the  centre.  The 
liquid  silver,  at  the  moment  of  passing  to  the  solid  state,  is 
agitated,  and  then  suddenly  becomes  quiet.  After  remaining 
motionless  awhile,  the  surface  breaks  up  into  several  lines  of 
fissures,  and  liquid  silver  flows  out  again,  renewing  the  original 
agitation.  Presently  the  gas  is  given  off  with  great  violence, 
and  numerous  little  protuberances  stud  the  whole  face  of  the 
mass.  Some  of  these  are  true  volcanic  cones.  They  have  a 
crater,  and  the  liquid  silver,  boiling  violently,  pours  out  through 
them  over  the  superficial  incrustation.  The  cones  gradually 
increase  in  height,  hj  the  accumulation  of  metal.  The  surface 
of  the  metallic  crust  on  which  they  rest  is  now  violently  agitated, 
being  heaved  up  and  falling  again  in  great  undulations.  At 
last  some  of  the  craters  close,  and  more  work  is  consequently 
thrown  upon  those  which  still  continue  to  give  exit  to  the  gas. 
The  funnels  are  now  lengthened,  and  proportionally  contracted. 
The  globules  of  silver  are  now  projected  with  greater  force, 
being  carried  beyond  the  furnace.  A  series  of  explosions 
accompanies  the  expulsion  of  these  ejected  masses.  The  last 
remainino;  crater  is  that  which  exhibits  this  volcanic  action  in 


SILVEK.  335 

its  greatest  energy.  It  is  a  remarkable  coincidence  with  the 
known  geological  history  of  volcanoes,  that  these  cones  are  not 
all  equally  active,  some  having  spent  their  force  and  become 
closed,  while  new  ones  are  rising.  During  this  action,  portions 
of  silver  are  shot  forth,  which  assume,  on  cooling,  cylindrical 
or  fantastic  shapes. 

LIQUATION. 

This  process,  which  is  more  commonly  known  as  sweating, 
is  based  on  the  various  fusibility  of  metals  and  their  different 
affinities  for  one  another.  It  is  sometimes  applied  to  the  sepa- 
ration of  the  easily  fused  metals  from  their  stony  matrices,  and 
sometimes  to  the  extrication  of  certain  metals  from  their  alloys. 

A  furnace  of  a  peculiar  construction  is  used  for  this  purpose. 
It  consists  essentially  of  two  walls  sloping  towards  each  other, 
upon  which  are  laid  the  liquation  or  refining  plates.  These  are 
plates  of  iron,  which,  like  the  walls,  incline  towards  each  other, 
leaving  an  opening  between  them,  through  which  the  melted 
metal  may  drip. 

This  process  is  applied  especially  to  the  reduction  of  the 
argentiferous  copper  of  Germany.  The  copper  having  been 
first  smelted,  is  mixed  with  lead,  in  the  proportion  of  3  or  4 
parts  of  the  former  metal  to  10  or  11  of  the  latter,  and  the 
resulting  alloy  is  broken  into  small  masses.  These  are  laid  on 
the  liquation  hearth,  and  the  proper  heat  applied  by  coals  which 
cover  them.  Most  of  the  lead  runs  down  into  the  chamber 
below,  carrying  the  silver  with  it,  and  leaving  on  the  hearth  the 
copper  alloyed  with  from  10  to  30  per  cent,  of  lead. 

CRYSTALLIZATION. 

This  process  of  refining  has  been  introduced  by  Mr.  Pattin- 
son,  of  Newcastle,  England.  It  is  exceedingly  economical,  the 
loss  of  lead  amounting  to  no  more  than  2  per  cent.,  so  that  it  is 
profitably  applied  to  alloys  too  poor  in  silver  to  be  submitted  to 
cupellation.  The  process  is  based  upon  the  behavior  of  an 
alloy  of  silver  and  lead  remaining  long  in  fusion. 

When  an  alloy  of  this  kind  is  allowed  to  cool  very  slowly. 


336      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

with  constant  stirring,  crystals  are  formed  -which  are  poorer  in 
silver  than  the  original  alloy.  The  liquid  metal,  therefore, 
retains  excess  of  silver.  These  crystals  may  be  lifted  out  and 
drained  as  fast  as  they  are  formed,  so  that  the  fused  metal  con- 
tains a  continually  increasing  proportion  of  silver.  By  this 
process,  the  poor  lead  is  brought  to  the  ordinary  standard  of 
alloys  designed  for  cupellation,  while  the  better  lead  is  made 
ten  times  richer.  The  necessary  loss  is,  therefore,  reduced  to 
one-tenth  of  what  it  is  under  the  old  process,  so  that  it  becomes 
j'g  of  one  per  cent,  instead  of  7  per  cent. 

The  practical  details  of  the  operation  are  very  simple.  In 
the  improved  method,  a  series  of  seven  pots  is  used,  each  of 
which  is  heated  by  a  separate  fire.  The  crystals  which  are 
formed  in  the  first  of  these,  and  which  still  contain  some  silver, 
though  much  less  than  that  which  remains  in  fusion,  are  lifted 
in  a  drainer  and  emptied  into  the  second  pot.  Here  a  second 
crystallization  takes  place,  which  results  in  a  farther  impover- 
ishment of  the  crystals.  These  are  transferred  to  the  third  pot 
of  the  series,  and  the  enriched  mass  returned  to  the  first.  This 
constant  shifting  of  the  products  of  each  crystallization  is  con- 
tinued till  pure  marketable  lead  is  taken  out  of  one  end  of  the 
apparatus  and  a  rich  alloy  of  lead  and  silver  from  the  other. 

HUMID   PROCESS. 

In  the  humid  way,  silver  is  separated  from  its  combinations 
with  other  metals  in  several  ways ;  the  two  most  important  of 
which  are  the  separation  of  the  metal  by  copper,  and  of  the  chlo- 
ride by  common  salt  or  hydrochloric  acid. 

When  silver  is  alloyed  with  copper  alone,  neither  of  these 
methods  presents  any  difficulty.  In  any  case,  the  alloy  is  dis- 
solved in  dilute  nitric  acid  with  the  aid  of  heat.  If  the  precipi- 
tation as  metallic  silver  is  determined  upon,  strips  of  pure  copper 
are  introduced  into  the  solution,  which  is  then  gently  warmed 
till  all  the  silver  is  deposited,  which  may  be  known  by  the  solu- 
tion no  longer  afibrding  a  precipitate  with  hydrochloric  acid. 
The  silver  is  thrown  down  in  a  pasty  form.  The  remainder  of 
the  copper  slips  is  then  removed,  and  the  precipitate  thoroughly 


SILVER.  337 

washed  in  warm  water.  It  is  then  digested  for  some  time  with 
ammonia,  in  order  to  remove  any  adhering  copper,  washed  again 
with  warm  water,  dried,  and  fused  with  a  little  borax  or  salt- 
petre. The  objections  to  this  process  are  that  other  metals 
besides  silver  are  precipitated  bv  metallic  copper. 

When  the  separation  of  silver  as  a  chloride  is  determined 
upon,  the  nitric  acid  solution  of  the  alloy  is  treated  with  dilute 
hydrochloric  acid,  or  with  chloride  of  sodium  (common  salt)  in 
solution,  so  long  as  a  precipitate  is  thrown  down.  A  white 
curdy  precipitate,  which  becomes  dark  on  exposure  to  light, 
makes  its  appearance,  and  slowly  subsides  to  the  bottom  of  the 
vessel.  Agitation  facilitates  both  the  formation  and  the  subsi- 
dence of  the  precipitate.  The  chloride  of  silver  is  now  re- 
peatedly washed  with  clear,  pure  water,  till  all  trace  of  acid  has 
disappeared.  The  water  poured  olF  after  each  washing  must  be 
transferred  to  a  deep  glass  jar,  and,  if  not  perfectly  clear,  must 
be  allowed  to  stand  for  several  hours  in  a  warm  place.  Should 
any  precipitate  form,  it  is  added  to  that  previously  obtained. 

The  reduction  of  the  chloride  to  metallic  silver  is  effected  in 
two  ways,  by  fusion  with  carbonate  of  potash,  or  by  dechlorin- 
izing  it  by  a  stream  of  hydrogen  gas.  In  attempting  the  re- 
duction by  the  first-named  method,  it  is  necessary  first  to  dry 
the  chloride  thoroughly,  and  then  to  rub  it  to  powder  in  a  stone 
mortar.  The  carbonate  of  potash,  in  the  proportion  of  2  to  1 
of  silver,  is  then  fused  in  a  black-lead  or  Hessian  crucible,  taking 
care  not  to  fill  it  more  than  half  full,  for  there  will  be  much  loss 
by  ebullition  should  this  precaution  be  neglected.  The  car- 
bonate of  potash  having  been  brought  to  a  state  of  fusion,  the 
chloride  of  silver  is  projected,  in  small  portions  at  a  time,  into 
the  melted  salt.  Violent  effervescence  takes  place,  in  conse- 
quence of  the  rapidity  with  which  the  carbonate  of  potash  is 
decomposed,  and  carbonic  acid  and  oxygen  gases  driven  off. 
The  result  of  the  double  decomposition  is,  that  the  carbonate 
having  lost  the  last  two  named  gases,  potassium  remains,  which 
combines  with  the  chlorine  of  the  silver  salt,  and  metallic  silver 
subsides.  At  first,  the  heat  should  not  be  higher  than  a  full 
red,  but,  so  soon  as  the  violence  of  the  action  has  ceased,  the 
temperature  is  increased  to  a  reddish  white,  in  order  to  insure 
22 


338      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

the  perfect  fusion  of  the  silver  and  its  complete  separation  from 
the  slag.  The  metal  may  then  be  most  conveniently  separated 
from  the  slag  by  pouring  it  into  water  from  a  height,  when  the 
chloride  of  potassium  is  at  once  dissolved  and  the  granulated 
silver  subsides.  Some  loss,  however,  is  occasionally  experienced 
in  this  way,  especially  if  the  metal  be  very  hot  and  in  large 
quantities,  when  it  sometimes  explodes  with  great  violence,  pro- 
jecting globules  of  silver  to  a  considerable  distance  beyond  the 
vessel. 

AVittstein  affirms  that  the  most  economical  method  of  reducing 
the  chloride  of  silver  is  to  heat  it  with  wet  charcoal.  He  mixes 
2  parts  of  the  chloride  with  1  part  of  moist  charcoal,  packs  the 
mixture  in  a  black-lead  crucible,  loosely  covered,  and  calcines  it 
till  half  an  hour  has  elapsed  after  the  cessation  of  the  evolution 
of  hydrochloric  acid  vapor.  When  cold,  he  extracts  the  silver 
from  the  mass  by  meaus  of  nitric  acid  of  1.20,  3  parts  of  the 
acid  being  required  for  two  of  the  chloride.  By  giving  the 
crucible  a  very  high  heat,  the  reduced  silver  will  be  fused  into 
globules,  which  can  be  separated  mechanically  from  the  re- 
maining charcoal.  The  reducing  power  of  the  charcoal  depends 
upon  the  hydrogen  it  contains. 

The  reduction  by  hydrogen  is  preferable  to  the  last  described 
method,  as  it  aifords  a  perfectly  pure  silver  without  any  percep- 
tible loss.  The  chloride  having  been  thoroughly  washed,  as 
already  described,  pieces  of  pure  iron  or  zinc  are  introduced  into 
it  and  sufficient  sulphuric  acid  to  disengage  hydrogen.  This 
gas  streams  up  through  the  chloride,  converting  its  chlorine  into 
hydrochloric  acid,  which  attacks  the  iron  or  zinc.  During  the 
formation  of  the  chloride  of  the  reducing  metal,  hydrogen  is 
again  set  at  liberty,  and  reduces  another  portion  of  silver,  by 
separating  the  chlorine  from  it  to  form  hydrochloric  acid.  This 
process  goes  on  continually,  till  the  entire  precipitate  is  decom- 
posed. The  silver  thus  reduced  is  in  a  state  of  exceedingly  mi- 
nute subdivision,  without  the  slightest  metallic  appearance,  but 
resembling  finely  divided  ashes  more  than  anything  else.  The 
metallic  lustre  of  silver  can,  however,  be  developed  by  pressing 
this  ash-colored  powder  with  any  smooth,  hard  substance,  such 
as  glass  or  polished  iron.     The  reduction  is  accomplished  in  a 


SILVER.  339 

day  or  two,  and  if  the  precipitate  is  in  a  state  of  sufficiently 
minute  division,  and  enough  sulphuric  acid  and  reducing  metal 
have  been  introduced,  the  reduction  will  be  complete.  It  can 
easily  be  determined  whether  any  chloride  remains  undecomposed 
by  digesting  the  precipitate  in  water  of  ammonia,  which  dis- 
solves the  chloride  and  lets  it  fall  again  on  saturation  with  an 
acid.  The  reduced  silver  must  be  washed  first  with  acidulated 
water  to  remove  any  small  adhering  particles  of  iron  or  zinc, 
and  then  with  pure  water.  After  the  washing,  the  silver  is 
thoroughly  dried,  and  fused  with  borax.  It  is  best  to  mix  the 
powdered  glass  of  borax  with  the  silver  and  project  it  in  small 
quantities  into  the  heated  crucible.  The  same  precautions 
should  be  observed  in  reference  to  the  heat  as  have  already  been 
described  under  the  head  of  Reduction  by  means  of  Carbonate 
of  Potash. 

This  process  is  performed  at  the  United  States  Mint,  on  about 
a  thousand  pounds  of  silver  a  day.  Zinc  is  there  preferred  to 
iron,  which  is  used  by  some  silver-workers,  on  account  of  the 
greater  facility  of  granulation,  the  greater  rapidity  of  reduction, 
and  the  greater  ease  with  which  the  residual  zinc  can  be  separated 
from  the  precipitated  silver.  Saltpetre  and  borax  are  used  in 
fusing  the  silver.  Without  any  special  pains,  by  this  process 
silver  is  obtained  of  a  fineness  of  995  to  997|  thousandths,  and 
may  be  easily  refined  in  the  pot  to  999  thousandths. 

Kessler  obtains  absolutely  pure  silver  by  dissolving  the  alloy 
with  copper  or  lead  in  nitric  acid,  diluted  with  20  times  its  bulk 
of  water,  and  adding  a  solution  of  protacetate  of  iron  till  a  pre- 
cipitate ceases  to  fall.  This  is  washed  till  the  mixings  no  longer 
give  a  precipitate  with  ferrocyanide  of  potassium.  The  silver  is 
so  entirely  thrown  down  that  common  salt  will  not  make  the  fil- 
tered solution  turbid.  The  protacetate  of  iron  precipitates  pla- 
tinum also. 

Lovel  uses  sugar  to  reduce  the  chloride.  He  boils  the  salt 
in  a  solution  of  sugar  in  water  of  potassa.  Gray  metallic  silver 
falls,  and  carbonic  acid  is  evolved. 

Rose  has  objected  to  the  process  with  chloride  of  sodium, 
that  the  precipitation  of  the  silver  is  not  complete,  this  salt,  as 
well  as  the  chlorides  of  potassium  and  ammonium,  retaining  some 


340      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  the  metal  in  solution.  This  objection,  hovfever,  has  weight 
only  "with  the  analytical  chemist,  as  the  loss  of  silver  is  so  small 
as  to  be  scarcely  perceptible  to  the  operator  who  is  preparing  it 
for  mechanical  purposes,  and  much  too  minute  to  pay  the  differ- 
ence in  cost  between  salt  and  muriatic  acid. 

It  has  been  farther  objected  that  mercury,  when  present  in  an 
alloy  of  silver,  is  precipitated  by  the  chlorides  along  with  the 
latter  metal.  Its  presence  can  be  recognized  by  the  altered  be- 
havior of  the  precipitated  chloride.  When  there  are  from  four 
to  five  thousandths  of  mercury  present,  the  chloride  does  not 
blacken  at  all,  but  remains  of  a  dead  white.  When  three 
thousandths  are  present,  there  is  no  marked  discoloration  in  the 
diffused  light  of  a  room.  With  two  thousandths  the  darkening 
is  slight,  and  with  one  thousandth  it  is  more  marked,  but  still 
much  less  intense  than  when  pure  silver  alone  has  been  subjected 
to  the  action  of  chlorine.  When  these  phenomena  are  present, 
it  is  best  to  purify  the  alloy  in  the  dry  way. 

One  of  the  most  troublesome  metals  to  the  chemist,  who  is 
attempting  the  separation  of  silver  from  its  alloy  by  this  humid 
process,  is  lead.  Very  minute  portions  of  this  metal  are  preci- 
pitated from  strong  solutions  by  hydrochloric  acid  or  the  chlo- 
rides, and  when  lai'ge  quantities  of  it  are  present,  its  chloride  is 
precipitated  from  quite  dilute  solutions.  When  there  is  but 
little  lead  in  the  alloy,  this  diflSculty  is  obviated  by  making  the 
solution  very  dilute,  and  precipitating  while  warm.  Should 
much  be  present,  it  will  generally  fall  with  the  silver,  and  then 
may  be  distinguished  by  its  obscure  crystalline  character,  and 
its  rapid  heavy  subsidence.  It  may  be  removed  by  repeatedly 
washing  the  mingled  precipitate  with  boiling  water,  in  which 
chloride  of  lead  is  soluble.  In  the  small  way,  the  two  chlorides 
may  be  separated  by  means  of  ammonia,  in  Avhich  the  silver-salt 
alone  is  soluble.  A  still  simpler  method  is  to  precipitate  the 
solution  of  silver-lead  with  a  solution  of  chloride  of  lead.  It  is 
more  convenient,  however,  to  treat  this  alloy  by  cupellation. 

Of  the  parting  of  silver  from  gold  it  is  not  necessary  here  to 
speak,  that  process  having  been  already  described  in  the  chap- 
ter on  Gold.  It  is  proper,  however,  to  state,  that  all  goldsmiths' 
silver  and  most  silver  coin  contain  gold,  which  makes  its  ap- 


SILVER.  341 

pearance  in  dark  jQocculi,  when  the  silver  is  dissolved  in  nitric 
acid.  The  separation  of  silver  from  platinum  will  be  treated  of 
under  the  head  of  the  latter  metal.  Its  separation  from  all 
other  metals  is  effected  with  greater  or  less  facility  by  the  pro- 
cesses already  described. 

SILVER,    NON-SALINE    COMPOUNDS,    AND   ALLOYS. 

Silver. — Silver  varies  in  appearance  according  to  the  manner 
in  which  it  has  been  obtained.  The  precipitated  powder  is,  as 
already  said,  gray,  devoid  of  lustre  but  assuming  the  brilliant 
appearance  of  metallic  silver  when  forcibly  compressed.  When 
fused  and  planished,  it  is  the  most  brilliant  of  the  metals,  and 
its  clear  white  color  is  too  well  known  to  need  any  description. 
It  is  harder  than  gold,  but  soft  enough  to  be  cut  with  a  knife, 
and  exceedingly  malleable  and  ductile.  It  may  be  reduced  to 
leaves  y^o^ooo  ^^  ^^  mch  in  thickness,  and  drawn  out  in  a  wire 
much  more  slender  than  the  finest  human  hair,  so  that  a  grain 
of  it  will  be  400  feet  in  length. 

It  does  not  oxidate  when  exposed  to  air  and  moisture,  but  in 
cities  it  gradually  becomes  covered  with  a  brownish-black  tar- 
nish, owing  to  the  formation  of  a  sulphuret  of  silver,  in  conse- 
quence of  the  action  upon  the  metal  of  the  sulphuretted  hydro- 
gen contained  in  the  atmosphere  of  populous  places.  In  salt  air 
it  also  tarnishes,  in  consequence  of  the  formation  of  a  chloride. 
Its  absorption  of  oxygen,  when  fused  in  the  open  air,  ha%  already 
been  described.  According  to  Brande,  5  per  cent,  of  copper 
prevents  this  action.  When  heated  to  redness,  without  melting, 
in  contact  with  glass  or  porcelain,  it  unites  with  oxygen,  and 
the  oxide  fuses  with  the  earthy  matters,  forming  a  yellow  enamel. 
When  silver  leaf  or  fine  wire  is  intensely  heated  by  galvanism 
or  the  oxyhydrogen  blowpipe,  it  burns  with  greenish-white  scin- 
tillations, which  are  very  vivid. 

The  only  pure  acids  which  act  on  silver  are  the  sulphuric  and 
nitric.  Both  of  them  oxidize  the  silver  at  the  expense  of  their 
own  oxygen,  and  afterwards  dissolve  it  in  the  remaining  unde- 
coraposed  acid.     Nitric  acid  is  its  proper  solvent. 

The  specific  gravity  of  fused  silver  is  10.47,  and  after  con- 


342      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

densation  under  the  hammer  or  press,  it  is  10.51.  It  fuses 
at  a  bright  red  heat  approaching  whiteness,  which  has  been 
variously  stated  at  1,280°,  1,860°,  and  1,873°  of  Fahrenheit's 
thermometer.  The  latter  number  is  probably  the  nearest  to  the 
truth.  Its  tenacity  is  intermediate  between  that  of  gold  and 
platinum.  Sickingen's  numbers  for  the  tenacity  of  these  three 
metals,  are,  for  gold,  15,  for  silver,  19,  and  for  platinum,  26 J. 

The  symbol  of  silver  is  Ag,  its  combining  number  1351.607 
on  the  oxygen,  and  108.306  on  the  hydrogen  scale. 

Suboxide  of  Silver,  Ag^O.  224.3. —Wohler  obtained  the 
citrate  of  this  oxide  by  exposing  citrate  of  silver  to  the  action 
of  hydrogen  gas  at  the  temperature  of  212°  F.,  one-half  the 
oxygen  being  liberated,  and  the  citric  acid  combining  with  the 
remaining  suboxide.  Faraday  obtains  it  by  exposing  an  ammo- 
niacal  solution  of  the  oxide  to  the  action  of  the  air,  when  the  sub- 
oxide falls.  When  its  solution  is  heated,  it  deposits  metallic  silver. 
Oxide  of  Silver,  AgO.  116.3. — This  oxide  is  prepared  by 
precipitating  a  solution  of  nitrate  of  silver  with  pure  potassa  or 
baryta,  Nvashing  thoroughly  and  drying  at  a  gentle  heat.  It  is 
a  brown  powder,  anhydrous,  becoming  black,  with  loss  of  oxy- 
gen on  exposure  to  the  sun.  Its  specific  gravity  is  7.143.  It 
is  slightly  soluble  in  water,  communicating  to  it  a  metallic  taste 
and  an  alkaline  reaction.  It  is  easily  reduced  by  heat  alone, 
or  by  hydrogen  at  212°  Fahrenheit. 

Oxide  of  silver  is  a  strong  base,  and  forms  salts  with  most  of 
the  aci4s.  These  salts  are  colorless  unless  the  acid  has  a  de- 
cided tint ;  they  have  a  styptic  metallic  taste,  and  are  poisonous. 
The  nitrate  and  some  others  are  soluble,  but  most  of  them  dis- 
solve only  partially  or  not  at  all  in  water,  but  readily  in  am- 
monia. The  metal  is  thrown  down  from  these  solutions  by  zinc, 
cadmium,  lead,  tin,  copper,  bismuth,  mercury,  iron,  tellurium, 
antimony,  arsenic,  phosphorus,  phosphorous  acid,  phosphuretted 
hydrogen,  copperas,  tin  salt,  and  many  organic  bodies.  When 
mercury  is  employed  for  this  purpose,  the  silver  is  deposited  in  a 
beautiful  arborescence,  known  as  the  Arbor  Dianse.  It  always 
contains  mercury.  Hydrochloric  acid  and  the  chlorides  throw 
down  insoluble  chloride  of  silver,  and  constitute  an  exceedingly 
delicate  test  for  the  metal,  rendering  opalescent  a  solution  which 


SILVER.  343 

contains  but  one  part  of  silver  in  300,000.  Hydriodic  and  hy- 
drobromic  acids  throw  down  a  yellowish  iodide  or  bromide  from 
strong  solutions.  Sulphuretted  hydrogen  and  alkaline  sulphurets 
precipitate  a  brownish-black  sulphuret,  soluble  in  strong  nitric 
acid.  Potassa  and  soda  throw  down  a  gray  oxide.  Ammonia 
gives  the  same  precipitate  and  redissolves  it  in  excess.  The 
carbonates  produce  a  white  precipitate.  The  precipitates  from 
arsenites  and  phosphates  are  yellow  ;  those  from  pyrophosphates 
and  metaphosphates,  white ;  from  chromates  and  arseniates, 
brownish-red  or  dark-crimson  ;  from  cyanides,  sulphocyanides, 
ferrocyanide  of  potassium,  and  oxalic  acid,  white ;  from  ferridcy- 
anide  of  potassium,  reddish-brown.  A  solution  of  oxide  of  silver 
in  ammonia  gradually  deposits  suboxide,  Ag02. 

Fulminating  Silver. — This  appears  to  be  a  compound  of  oxide 
of  silver  with  ammonia.  It  is  formed  by  precipitating  oxide  of 
silver  with  lime-water,  washing  it  on  a  filter,  and  then  spreading 
it  on  bibulous  paper,  to  absorb  moisture  from  it.  When  nearly 
dry,  water  of  ammonia  is  poured  upon  it,  and  allowed  to  stand 
on  it  for  ten  or  twelve  hours,  at  the  end  of  which  period  most 
of  the  originally  precipitated  oxide  has  disappeared,  having  been 
dissolved  in  the  ammonia.  There  remains,  however,  a  black 
powder,  which  is  carefully  removed  and  spread  out  upon  several 
pieces  of  bibulous  paper  to  dry.  It  may  be  obtained  more 
expeditiously  by  dissolving  the  nitrate  of  silver  in  ammonia  and 
precipitating  by  caustic  potash. 

This  is  a  terribly  explosive  compound.  When  pressed  by  a 
hard  body,  while  still  moist,  it  detonates  with  great  violence. 
In  its  dry  state  it  is  still  more  dangerous.  Heat,  electricity, 
touch,  even  the  agitation  of  the  powder  induced  by  pouring  it 
out,  or  by  stirring  it  with  a  feather,  produce  explosion.  Many 
persons  have  been  seriously  injured  by  it ;  some  have  been  killed. 
Nor  have  these  accidents  been  confined  to  the  inexperienced 
alone.  Professor  Hare,  of  the  University  of  Pennsylvania,  was 
severely  wounded  by  the  explosion  of  a  quantity  of  this  sub- 
stance, whilst  he  was  pouring  it  upon  the  head  of  a  hammer,  to 
exhibit  its  properties  to  his  class.  It  ought  always  to  be  made 
in  small  quantities,  and  kept  in  little  paper  boxes,  with  paste- 
board covers  laid  loosely  on  them.     It  should  never  be  kept  in 


344      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

a  glass  bottle,  because,  let  the  precautions  observed  be  what 
they  may,  small  fragments  of  the  powder  are  apt  to  adhere  to 
the  neck  in  pouring  it  out,  and  then  the  introduction  of  the 
stopple  is  followed  by  an  explosion.  Nay,  more,  it  is  liable  to 
explode  from  the  slight  friction  produced  by  the  passage  of  the 
particles  over  the  glass  during  the  act  of  pouring  it  out,  and 
serious  accidents  have  occurred  from  the  jarring  of  the  shelves 
in  which  it  is  kept  by  the  motion  of  a  passing  cart.  The  solu- 
tion deposits  black  crystalline  particles,  which  are  even  more 
explosive,  detonating  by  simple  agitation  of  the  liquid. 

Peroxide  of  Silver. — When  a  voltaic  current  is  passed  through 
a  weak  solution  of  nitrate  of  silver,  needles  of  a  metallic  lustre, 
interlacing  with  one  another,  are  deposited  at  the  positive  pole. 
When  thrown  into  hydrochloric  acid,  it  causes  disengagement 
of  chlorine  at  the  same  time  that  chloride  of  silver  falls.  Pro- 
jected into  ammonia,  a  rapid  evolution  of  nitrogen  gas,  attended 
with  a  hissing  sound,  takes  place,  so  that  the  whole  liquid 
froths.  A  little  of  the  oxide,  mixed  with  phosphorus,  and  struck 
with  a  hammer,  detonates.  With  heat  it  decrepitates,  and 
becomes  metallic  silver. 

Sulphuret  of  Silver,  AgS.  124.1. — This  compound  of  silver 
is  found  native  as  silver  glance  or  vitreous  silver.  It  may  be 
made  by  simply  fusing  the  elements  together,  or  by  precipitating 
a  solution  of  silver  with  sulphuretted  hydrogen  or  by  alkaline 
sulphuret.  It  is  spontaneously  formed  Avhenever  silver  is  brought 
in  contact  with  a  sulphuret,  either  gaseous  or  liquid.  So  strong 
is  the  affinity  of  this  metal  and  sulphur,  that  it  has  been  used  as 
a  convenient  blowpipe  test  for  the  presence  of  sulphuric  acid. 
The  suspected  sulphate  is  fused  with  soda  and  charcoal  in  the 
reducing  flame.  This  process  gives  rise  to  a  sulphuret  of  sodium, 
which  is  soluble  in  water.  The  fused  bead  removed  and  laid  on 
a  bright  silver  surface,  as  the  face  of  a  coin,  is  then  wet  with 
pure  water,  allowed  to  remain  a  moment  in  contact  with  the 
metallic  surface,  and  then  washed  away.  A  dark  spot  of  sul- 
phuret of  silver  remains  on  the  metal.  It  has  already  been  said 
that  the  air  of  cities,  which  contains  sulphuretted  hydrogen, 
tarnishes  silver.  It  is  well  known,  also,  that  a  spoon  of  this 
metal  becomes  speedily  blackened  in  contact  with  eggs  or  mus- 


SILVER.  345 

tard,  on  account  of  the  sulphur  present  in  those  substances. 
This  tarnish  is  removed  with  great  facility  by  the  use  of  chame- 
leon mineral,  made  by  fusing  peroxide  of  manganese  Avith  nitrate 
of  potassa. 

Sulphuret  of  silver  is  dark  brown,  soft  enough  to  be  cut  with 
a  knife,  and  slightly  malleable.  Calcination  decomposes  it, 
driving  off  the  sulphur,  as  sulphurous  acid,  the  metallic  silver 
remaining.  Nitric  acid  decomposes  it,  the  resulting  compound 
being  nitrate  of  silver  and  sulphuric  acid,  while  free  sulphur 
floats  in  the  solution.  Sulphuret  of  silver  is  a  powerful  sulpho- 
base,  since,  though  heated  to  redness,  it  retains  the  volatile 
sulphurets,  which  are  usually  driven  off  from  their  other  com- 
binations at  that  temperature.  The  percentage  of  the  elements 
constituting  this  compound  has  been  stated  at — silver,  87.04; 
sulphur,  12.96;  by  calculation,  silver  88.51,  sulphur  11.49. 

Carburets  of  Silver. — When  silver  is  ignited  with  lampblack, 
AgjC  is  formed.  Strong  ignition  of  cyanide  of  silver  produces 
AgC.  Pyroracemate  of  silver,  heated  for  a  long  time  in  a  water- 
bath  and  distilled,  yields  AgCj. 

Pliosphuret  of  Silver. — This  compound  may  be  formed  by 
igniting  silver  and  phosphorus  together  in  a  closed  crucible. 
Ignition  of  the  phosphate  of  silver  with  charcoal  produces  the 
same  substance.     It  is  white,  granular,  sectile,  and  brittle. 

Siliciuret  of  Silver. — This  is  a  combination  of  silver  with 
silicon,  and  is  formed  by  heating  under  an  alkaline  glass  flux,  a 
mixture  of  silver  powder,  charcoal,  and  silicic  acid. 

ALLOYS    OF   SILVER. 

Antimony,  arsenic,  bismuth,  zinc,  and  tin,  form  brittle  alloys 
with  silver.  The  latter  metal,  in  very  small  quantity,  destroys 
the  ductility  of  silver.  An  easy  method  of  separating  these  two 
metals  is  to  laminate  the  alloy  in  thin  plates  and  distil  it  with 
corrosive  sublimate.  The  volatile  bichloride  of  tin  passes  over 
and  condenses  in  the  receiver.  They  may  also  be  separated  in 
the  humid  way. 

Manganese  and  silver  form  an  alloy.  Silver  and  lead  unite 
in  all  proportions,  and  are  easily  separated  by  cupellation.    Iron 


346      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

and  silver  fuse  together  and  form  an  alloy  ■which  cannot  be 
resolved  by  cupellation,  but  which  is  easily  decomposed  by  solu- 
tion in  nitric  acid  and  precipitation  with  hydrochloric  acid,  or  a 
soluble  chloride.  The  silver  may  also  be  separated  from  this 
combination  by  fusion  with  borax  or  saltpetre.  Steel  combines 
with  silver,  forming  a  very  hard  alloy,  silver-steel,  which,  after 
heating,  contains  1  part  of  silver  in  500.  Silver  alloys  with  the 
precious  metals,  the  malleability  of  which  it  diminishes,  except 
in  the  case  of  gold  and  iridium. 

Most  of  the  silver  of  commerce  is  alloyed  with  a  very  minute 
portion  of  gold,  and  Pettenkofer  asserts  that  all  the  commer- 
cial metal  which  has  not  been  submitted  to  chemical  purification, 
contains  platinum  also. 

An  alloy  of  silver  with  one-tenth  or  one-twelfth  of  copper,  is 
the  standard  of  coin  in  most  countries.  It  is  harder  and  more 
durable  than  silver  alone.  "When  boiled  with  a  solution  of  cream 
of  tartar  and  common  salt,  or  when  scrubbed  with  water  of 
ammonia,  the  superficial  particles  of  copper  are  removed,  and  a 
surface  of  pure  silver  is  left.  A  combination  of  95  parts  of 
silver  to  5  of  copper  constitutes  the  metal  for  medals  and  for 
the  finest  silver  plate.  Silver  solder  is  composed  of  different 
proportions  of  materials,  according  as  it  is  designed  for  the 
finest  or  for  common  work.  That  used  with  95  per  cent,  silver 
is  composed  of  silver,  66.Q  ;  copper,  23.4 ;  zinc,  10.  The  com- 
mon silver  solder  is  made  of  silver,  66.6  ;  copper,  30 ;  brass, 
3.4.  The  last  ingredient  renders  it  an  uncertain  compound ; 
for,  independently  of  the  fact  that  this  is  an  alloy  of  no  definite 
proportions,  brass  always  loses  zinc,  and  becomes  richer  in 
copper  after  every  fusion. 

The  following  table  of  silver  coin  is  taken  from  the  same 
source  whence  we  derived  our  table  of  gold  coin  : — 


SILVER. 


347 


Table  of  Silver  Coins. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Argextine  Republic. 

Dollar  of  Rio  de  la  Plata, 

1828 

380 

862 

88  2 

((                       a 

'< 

411 

822 

91 

<£                                .< 

(f 

418 

800 

90 

Half-dollar  of  Rio  de  la  Plata, 

1815 

205 

888 

49 

Quarter-dollar  of  Rio  de  la  Plata, 

1813-16 

98 

886 

23  4 

Dollar  of  Argentine  Republic, 

1838-39 

388 

928 

97 

a                          a 

'< 

427 

894 

1  02  8 

a                          a 

(< 

412 

915 

1  01  5 

The  extreme  irregularity  of  the  coinage 

of  this  re- 

public,  and  of  the  old  Spanish  proTince  of  Rio  de 

la  Plata,  and  its  variations  in  the  same  year,  as 

seen  by  the  above  table,  render  it  impo 

^sible  to  es- 

timate  its  value  in  any  way  but  by  direct  analysis. 

Austria. 

Rix  dollar  of  Maria  Theresa, 

1753-80 

430 

835 

96  7 

"         of  Joseph  XL, 

1780-89 

481 

835 

97 

"        of  Leopold  II.  and  Francis  I., 

1790-1800 

432 

835 

97  2 

a                              11                                    a 

1834 

432 

833 

^97 

Rix  and  kremnitz  dollar  of  Ferdinand  I., 

1839-40 

432.5 

834 

97  2 

Florin  of  Joseph  II., 

1788 

215 

835 

48  4 

"      of  Francis  I., 

1834 

216 

838 

48  8 

"      and  kremnitz  florin  of  Ferdinand  I 

,    1839-40 

216.5 

834 

48  7 

Brabant  crown  of  Francis  I., 

1793-99 

454 

875 

1  07 

20  kreutzer  of  Francis  I., 

1884 

103 

580 

16  1 

"          of  Ferdinand  I., 

1840 

103 

582 

16  2 

10  ki-eutzer. 

60.5 

500 

08  1 

Scudo  of  Ferdinand  I. , 

1839 

401.5 

902 

97  6 

Lira, 

67 

900 

16  2 

Quarter-lira, 

25 

006 

04  1 

Badex. 

Specie  dollar  of  Charles  Frederick,  Margrave,  1765-78 

428 

883 

96  1 

Crown  of  Interregnum, 

1813-16 

455 

875 

1  07  3 

"       of  Louis,  Grand  Duke, 

1819-29 

455 

877 

1  07  5 

"       of  Leopold, 

1831-34 

456 

887 

1  07  7 

Two  guilder  of  Louis,  Grand  Duke, 

1822-25 

392 

755 

79  8 

Guilder  of  Leopold, 

1837-39 

164 

900 

39  7 

Bavaria. 

Specie  dollar  of  Maximilian  Joseph  and 

Charles  Theodore, 

1755-1810 

430 

833 

96  5 

Specie  dollar  of  King  Maximilian, 

430 

835 

90  7 

Crown  (palatinate)  of  Charles  Theodore, 

397 

995 

1  06  4 

"      of  Kings  Maximilian  and  Louis, 

1809-32 

455 

875 

1  07  2 

Florin  (palatinate), 

1758 

198 

995 

53  1 

"      of  King  Louis, 

1839 

163.5 

900 

39  6 

Six  ki-eutzers  of  King  Louis, 

1833 

41 

320 

03  5 

348  CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Silver  Coins — Continued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.   c.  m. 

Belgium. 

Crown  of  Joseph  II.  and  Leopold  II., 

1781-92 

453 

875 

1  06  7 

"       of  Francis  II., 

1793-1800 

454 

878 

1  07 

FiTe  francs  of  Leopold  I., 

1833-35 

385.5 

895 

93  1 

Franc  of  Leopold  I., 

1833-35 

77 

897 

18  6 

Two  francs  same  fineness  as  five  francs;    fractions 

like  the  franc. 

Bolivia. 

Dollar, 

1827-37 

416.5 

902 

1  01  2 

t( 

1840 

417 

900 

1  01 

Half-dollar, 

1827-28 

208 

903 

50  5 

" 

1830 

208 

670 

37  5 

Quarter-dollar, 

1827-28 

104 

900 

25  2 

(( 

1830 

103.5 

675 

18  8 

Brazil. 

640  reis  of  Joseph  I., 

1750-77 

274 

915 

67  5 

"        of  Maiia  I.  and  Peter  III., 

1777-80 

267 

903 

64  9 

"        of  Maria  I., 

1780-87 

274 

903 

66  6 

<(                 (( 

1800-04 

294 

903 

71  4 

«'       of  John,  Regent, 

1804-16 

284 

903 

69 

of  John  VL, 

181G-21 

275 

910 

67  4 

'<        of  Peter  I., 

1822-26 

276 

905 

67  2 

320  reis  of  John,  Regent, 

1804-16 

132 

910 

32  3 

1200  reis  of  Peter  II., 

1837 

414 

891 

99  4 

800      <' 

1838 

276 

891 

66  2 

400      " 

1837 

138 

886 

33 

The  other  coins  of  the  same  dates  are  of  the  same 

fineness. 

Britain. 

Shilling  of  George  I., 

1721-23 

87 

930 

21  8 

"       of  George  II., 

1727-46 

90 

930 

22  5 

"       of  George  III., 

1787 

92 

926 

22  9 

((                (( 

1816-17 

86 

934 

21  6 

"        of  George  IV., 

1820-29 

86.5 

930 

21  7 

of  AVilliam  IV., 

1831 

87 

930 

21  8 

"       Victoria, 

1838-40 

87 

925 

21  7 

Crown  of  George  IV., 

1822 

435 

930 

1  07 

The  other  pieces  are  proportional,  the 

fineness  being 

the  same  for  the  same  date.     The  bank  tokens  are 

dollars  restamped. 

Brunswick. 

Florin  of  Anthony  Ulrich, 

1704 

201 

997 

54 

"      (Leipzig)  of  Charles, 

1764 

198 

997 

53  2 

*'      of  Charles  William  Ferdinand, 

1789-1800 

263 

750 

53  1 

Specie  thaler  of  Charles  and  Charles  William 

Ferdinand, 

1764-90 

428 

833 

96 

Thaler  of  William, 

1838 

343 

750 

69  3 

J  thaler  of  Charles, 

1764-75 

78 

564 

11  8 

"       of  Charles  William  Ferdinand, 

1780-92 

78.5 

561 

11  9 

SILVER. 

Table  of  Silver  Coins — Qontinued. 


349 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Central  America. 

Dollar,                                                                 1824-36 

415 

899 

1  00  1 

Chili. 

Dollar, 

414 

907 

1  01 

The  coinage  of  the  last  two  counti-ies  are  averaged. 

The  standai'd  of  the  Chilian  dollar  ranges  from  905 

to  911  thousandths. 

Colombia. 

Dollar  of  eight  reals,                                         1819-21 

363* 

730 

71  4 

of  Bogota,                        1835-36 

417f 

910 

1  02  2 

"             "           of  New  Granada,                   1839 

356 

080 

65  2 

2  reals  of  Caraccas  and  Cundinamarca,            1815-21 

74 

690 

13  8 

\  Real  of  Caraccas,                                            1829-30 

8.5 

795 

01  8 

Denmark. 

Specie  daler  of  Christian  VII.,                         1769-77 

444 

875 

1  04  6 

"           of  Frederick  VI., 

445 

877 

1  05  1 

60  schillings  Holstein  of  Christian  VII.,           1787-94 

444 

878 

1  05 

40         "         or  two-thirds,  of  Christian  VII.,  1787-97 

295 

878 

69  8 

10         "         of  Christian  VIL,                           1787-89 

93 

670 

16  8 

\  specie  daler  of  Christian  VIII.,                  1798-1801 

113 

670 

20  8 

Rigsbank  daler  of  Frederick  VI.,                      1813-39 

222.5 

877 

52  6 

32  skillings  of  Frederick  VI.,                                   1820 

93.5 

692 

17  4 

Egypt. 

The  first  date  given  for  these  coins  is  the  year  of  the 

Hegira,  the  second  the  Christian  era. 

Yismilik,  or  ^  piasti-e,  of  Selim  III.,          1216  (1801) 

96 

372 

09  6 

Real,  or  20  piastres  of  Abdul  Majeed,       1255  (1839) 

430 

836 

96  8 

Nasf,  or  10  piastres,  of  Abdul  ]Maieed,      1255  (1839) 

215 

832 

48  2 

Ruba,  or  5  piastres,  of  Mahmoud'll.,        1252  (1836) 

107.5 

850 

24  6 

Ghersh,  or  piastre,  of  Abdul  M.njeed,         1255  (1839) 

21 

842 

04  8 

Ashreena,  or  20  paras,  of  Abdul  Majeed,  1255  (1839) 

10.5 

843 

02  4 

France. 

Crown  of  Louis  XV.,                                          1726-73 

440 

912 

1  08  1 

"      of  Louis  XVL,                                        1774-92 

444 

912 

1  09  1 

Half-crown  of  Louis  XV.,                                   1726-73 

212 

912 

52  1 

of  Louis  XVL,                                1774-92 

220 

912 

54 

Thirty  sols  of  Louis  XVL,                                        1792 

153 

667 

27  5 

Fifteen  sols  of  Louis  XVL,                                       1792 

77 

662 

13  7 

Six  Uvres  of  Louis  XVL,                                           1793 

445 

912 

1  09  3 

Five  francs  of  year  IV.   of  Republic,   and 

Bonaparte,  1st  Consul,            1803-04 

383 

902 

93  1 

"           of  Napoleon,  Emperor,                  1804-14 

383.5 

902 

93  2 

of  Louis  XVIIL,                            1815-24 

384 

902 

93  3 

of  Charles  X.,                                1825-30 

384.5 

902 

93  4 

"           of  Louis  Philippe,                 1831  and  seq. 

385 

899 

93  2 

The  standard  of  the  smaller  French  coins  since  the 

commencement  of  Louis  Philippe's  reign,  when  the 

humid  assay  of  silvei-,  invented  by  Gay-Lussac,  was 

introduced  into  the  French  mints,  has  been  900. 

*  Varies  from  849  to  854  in  fineness,  and  from  343  to  382  in  weight, 
■j-  Varies  in  fineness  from  907  to  917. 


350   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Silver  Coins — Continued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Greece. 

Five  drachm  of  Otbo, 

1833 

345 

900 

S3  6 

Draclime  of  Otho, 

1832-33 

68.5 

902 

16  6 

GciANA  (British). 

Dollar  of  three  guilders  of  George  III., 

1809 

359 

824 

79  7 

Guilder  of  George  III., 

1816 

119 

825 

26  4 

"      of  William  IV., 

1832 

119.5 

819 

26  4 

Haxover. 

Specie  thaler  of  Geoi-ge  III., 

1766 

449 

896 

1  08  3 

Florin  of  George  III.,                  1783-97  and  1807-1 4 

201 

995 

53  9 

((                 (1 

1801 

266 

753 

54 

"      of  George  IV., 

1825 

202 

996 

54  2 

Hepse  Cassel. 

Specie  thaler  of  Frederic  II., 

1766 

430 

836 

96  8 

Thaler  of  Frederic  II., 

1778 

360 

750 

72  7 

"      of  William  IX., 

1789 

291 

885 

69  4 

<'      of  William  II.  and  Frederick  William, 

1832-37 

341.5 

748 

68  8 

J  thaler  of  William  II., 

1824-27 

130.5 

660 

23  2 

\  thaler  of  William  II., 

1823-30 

81 

505 

11 

' '       of  William  II.  and  Frederick  William, 

1833-36 

82 

525 

11  6 

Hesse  Darmstadt. 

Specie  thaler  of  Louis  I., 

1809 

432 

833 

96  9 

Crown  of  Louis  I., 

1825 

455 

875 

1  07  2 

Gulden  of  Louis  II., 

1838-39 

164 

900 

39  8 

Two  thalers  of  Louis  II., 

1839 

574 

900 

1  39  1 

HiNDOSTAN. 

Sicca  rupee  of  Mogul  Empire,  Shah  Alum, 

177 

938 

44  7 

"                          "               Arcot, 

1782 

177 

958 

45  7 

"           of  Bengal,  19th  sun, 

179 

980 

47  2 

It                                         a 

1818 

192 

920 

47  6 

Rupee  of  Bombay, 

1818 

179 

920 

44  4 

" 

1818-40 

180 

917 

44  5 

Quarter-pagoda  of  INIadras, 

164 

900 

39  8 

Double-fauam  of  Southern  India, 

28 

909 

06  9 

Fanam  of  Southern  India, 

14 

920 

03  5 

Malay  Archipelago. 

Silver  rupee  of  Dutch  government  of  Java, 

1783 

200 

833 

45 

<(                        <(                     ii 

1796 

200 

663 

35  7 

Guilder  of  Dutch  government, 

1820 

166 

898 

40  2 

tt                    (t 

1839 

155 

944 

39  4 

Ducatoon  of  Dutch  goverament,                     1 

766-1804 

500 

938 

1  26  3 

Half-guilder  of  Dutch  government. 

1826 

83 

898 

20  1 

Quarter-guilder  of  Dutch  government. 

1840 

62.5 

569 

09  6 

Mauritius. 

Ten  livres, 

1810 

414 

833 

92  5 

SILVER. 

Table  of  Silver  Coins — Continued. 


351 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Mecklenburg  Schwerin 

Florin  of  Frederick  Francis, 

1790-1808 

265 

753 

53   7 

"      of  Paul  Frederick, 

1839  and  seq. 

203.5 

988 

54  1 

Eight  schilling  of  Frederick  Francis, 

1827 

103 

440 

12  2 

jMexico. 

Dollar  of  Mexico,  Augustin,  Emperor, 

1822-23 

416 

898 

1  00  6 

"      of  Mexican  Republic, 

1830-34 

416 

901 

1  01 

(<                ><              (( 

1835 

416 

906 

1  01  5 

<t                                  C(                              <( 

1836 

416.5 

904 

1  01  4 

<<                     <(                   (( 

1837 

416.5 

903 

1  01  3 

((                         ti                     a 

1840-41 

416.5 

902 

1  01  2 

"      of  Zacatecas, 

1834-35 

415.5 

896 

1  00  3 

i(                <« 

1836 

416.5 

898 

1  00  7 

((                (< 

1837 

408 

895 

98  4 

<<                (< 

1840 

414 

895 

99  8 

((                i< 

1841 

414 

897 

1  00 

"      of  Guanaxuato, 

1832-35 

416 

894 

1  00  2 

<<                (1 

1837 

412.5 

900 

1  00 

((                (( 

1838 

417 

901 

1  01  2 

((                li 

1840-41 

417 

896 

1  00  7 

"      of  Durango, 

1833-34 

415 

904 

1  01  1 

H                                 It 

1837-39 

417 

902 

1  01  3 

*'      of  Potosi, 

1835 

417 

902 

1  01  8 

H                                  1( 

1837-41 

416.5 

901 

1  01  1 

"      of  Chihuahua, 

1833 

417 

899 

1  01  1 

(<                                  14 

1840-41 

420 

907 

1  02  6 

"      of  Guadalaxara, 

1832 

416.5 

883 

99  1 

<(                            u 

1835 

416 

870 

94  2 

(<                <i 

1835 

416.8 

884 

97  5 

((                << 

1835 

416.5 

895 

99  2 

(<                                  K 

1840 

417 

904 

1  00  4 

Hammered  dollar, 

1811-18 

404 

880 

95  4 

Cast  dollar, 

417 

916 

1  03 

Vargas  dollar, 

1811-12 

405 

890 

97  1 

Morelos  dollar. 

1812-13 

407 

880 

96  4 

Half-dollar  of  Mexico, 

1827 

207 

905 

50  4 

"          of  Zacatecas, 

1831-36 

206 

898 

49  8 

"          of  Guanaxuato, 

1835-38 

206 

901 

50 

Quarter-dollar  of  Mexico, 

1825-28 

102.5 

902 

25 

"                     "         agacJiado, 

1824 

101 

898 

24  4 

it                     It 

1824 

100 

900 

24  2 

<<                     It 

1832-34 

103 

893 

24  6 

"            of  Zacatecas, 

1825-30 

103 

897 

24  7 

it                      it 

1832-35 

105 

898 

25  4 

Milan. 

Scudo,  six  liras,  of  Maria  Theresa, 

1778 

352 

898 

85  1 

"           "           of  Ferdinand  I., 

1839 

401.5 

902 

97  6 

Lira  of  Maria  Theresa, 

1780 

95  • 

550 

14  1 

"   of  Ferdinand  I., 

1809 

67 

900 

16  2 

"   of  Napoleon, 

1805-14 

76 

902 

18  5 

Quarter-lira  of  Francis  I., 

1822 

24.5 

590 

03  9 

"          of  Ferdinand  L, 

1839 

25 

600 

04  1 

352      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Silver  Coins — Continued. 


Nation. 

■Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

(1.    c.  m. 

Naples  and  Sicily. 

Scudo  of  Ferdinand  IV., 

1783 

390 

900 

94  5 

((                  (( 

1786-98 

422 

835 

94  9 

"      of  Ferdinand  IV.  and  Mary  Caroline,         1791 

422 

842 

95  7 

"      of  Sicily,  Ferdinand, 

1785-99 

419 

830 

93  7 

"      of  Republic  and  Joseph  Napoleon, 

1799-1805 

422 

835 

94  9 

"      of  Sicily,  Ferdinand  III., 

1810 

420 

835 

94  5 

"      of  Ferdinand  II., 

1831-33 

426 

830 

95 

Silver  ducat  of  Ferdinand  IV., 

1784-85 

348 

842 

78  9 

Carlin  of  Ferdinand  IV., 

1791-95 

34 

835 

7  6 

Lira  of  Joachim  Napoleon, 

1810 

76 

900 

18  5 

Netheeland.s. 

Ducatoon  of  William  V.,  Stadth older. 

17GG-95 

500 

938 

1  26  3 

Rix  doUar             "                     " 

" 

428 

872 

1  00  5 

"         of  Louis  Napoleon, 

1806 

436 

881 

1  03  5 

<(                        f( 

1808 

408 

912 

1  00  2 

Guilderof  William  v.. 

1766-95 

161 

912 

39  5 

"      of  Batavian  Republic, 

1796-1805 

157 

904 

38  2 

"      of  William  L, 

1816-38 

166 

896 

40  1 

25  cents  of  William  I., 

1824-30 

65 

569 

10 

Persia. 

Hazar-dinar  of  Fatha  Ali, 

106 

952 

27  1 

Sahib-koran  of  Fatha  Ali,                           '. 

222  (1807) 

159 

945 

40  4 

Peru. 

Dollar  of  Lima, 

1822-35 

416 

901 

1  01 

<(                     i; 

1837-38 

415 

904 

1  01 

<(                             iC 

1841 

415 

899 

1  00  5 

"      of  Cuzco, 

'1837-38 

414 

904 

1  00  8 

Half-dollar  of  Cuzco, 

1835 

208 

650 

36  4 

<<                  <f 

1836 

207 

667 

37  2 

"          ofArequipa, 

1838 

206 

660 

36  6 

Quarter-dollar  of  Lima, 

1828-32 

105 

900 

25  4 

"            of  Cuzco, 

1827 

105 

902 

25  5 

<<                    <( 

1835 

102 

654 

18 

Poland. 

Convention  thaler  of  Stanislaus  Augustus, 

1784 

430 

833 

96  5 

Thaler  of  Stanislaus  Augustus, 

1794 

370 

688 

68  6 

Zloty  of  Nicholas  I., 

1838 

48 

872 

11  3 

Portugal. 

Cruzado  of  Maria  I.  and  John  VI., 

1795-1826 

222 

900 

53  8 

"        of  Maria  II., 

1833 

226 

908 

55  3 

12  macutas  of  Maria  I.  (African  colonies) 

1789 

271 

896 

65  4 

Crown  of  1000  reis  of  Maria  II., 

1838 

456 

912 

1  12 

Piece  of  200  reis  of  Maria  II., 

1838 

91 

920 

22  6 

6  vintems  of  Maria  II., 

1833 

55 

898 

13  3 

SILVER. 

Table  of  Silver  Coins — Continued. 


353 


Prussia. 
Thaler  of  Frederick  II., 


of  Frederick  William  II., 
of  Frederick  William  III., 


1750 

1764-86 

1789-96 

1798-1803 

1813-19 

«'  "  "  1823-31 

ConTention  thaler  of  Frederick  William  II.  (for 

Brandenburg),  1795 

f  piece  of  Fred.  William  II.  (for  Brandenburg),  1797 

I  thaler  of  Frederick  II.,  1768-80 

"       of  Frederick  William  II.,  1786-97 

"       of  Frederick  William  III.,  1809 

\  thaler  of  Frederick  II.,  1764-73 

"       Frederick  William  II.,  1796-97 

"       Frederick  William  III.,  1801-18 

1822-28 


Rome. 
Scudo  of  Pius  VI., 
"      of  Republic, 
"      of  Senate  of  Bologna, 
"      of  Pius  VII., 

a  it 

"      of  Gregory  XVI., 
Testoon  of  Pius  VI. , 
"       of  sede  vacante, 

Russia. 
Rouble  of  Peter  the  Great, 
"      of  Catharine  I., 
*'      of  Elizabeth, 
"      of  Catharine  II., 
"      of  Paul  L, 
"      of  Alexander  I., 
"      of  Nicholas, 
10  zlots  of  Nicholas, 
20  copecks  of  Alexander  I., 


"  of  Nicholas, 

30  copecks  of  Nicholas, 

Sardinia. 

Scudo  of  Victor  Amadeus, 

"  "  (island), 

"      of  Republic  of  Genoa, 
"      of  Ligurian  Republic, 

Five  francs  of  Republic, 

Five  lire, 

Lii'a  of  Republic  of  Genoa, 

23 


1799 
1797 
1800-02 
1815 
1835 
1796 
1830 


1724 
1725 
1750 
1775 
1799 
1801-14 

1837  and  seq. 
1835 
1802 
1810 
1813 

1837  and  seq. 
1838 


1773 

1773 
1796 
1798 
1800 


1794 


Weight. 

Fineness. 

Grains. 

Thous. 

338 

754 

340 

750 

340 

749 

340.5 

745 

341 

748 

343 

750 

430 

830 

265 

750 

126 

668 

126 

670 

126 

667 

78 

519 

80 

515 

80.5 

517 

81.5 

526 

408 

913 

408 

899 

456 

842 

408 

913 

408.5 

925 

415 

900 

120.5 

913 

122 

925 

432 

729 

418 

736 

398 

792 

360 

757 

323 

870 

318 

875 

320 

875 

486 

871 

62 

875 

72 

760 

63 

877 

65 

875 

94 

872 

540 

906 

301 

896 

512 

889 

512 

885 

384 

892 

385 

902 

62 

889 

68  6 
68  7 
68  6 
08  3 

68  7 

69  3 


96 

53 

22 

22 

22 

10 

11 

11  2 

11  5 


00  4 
98  8 
03  4 

00  4 

01  8 
00  6 

29  6 

30  4 


84  8 
82  9 
84  9 
73  4 
75  7 
75 

75  4 
14 

14  6 
14  7 

14  0 

15  3 
22  1 


21  8 
87  1 

22  6 
22 

92  3 

93  5 
14  8 


354     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Table  of  Silver  Coins — Continued. 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

d.    c.  m. 

Saxoxy. 

Specie  thaler  of  Frederick  Augustus  XL, 

1763 

428 

842 

97  1 

"           of  Frederick  Ciiristian, 

1763 

430 

839 

97  2 

1 

764-1816 

432 

835 

97  1 

" 

1818-36 

430 

834 

96  6 

"            ofGross-herzogSachseii(Weimar),1815 

477 

755 

97 

Half-specie  tlialer  of  Fred.  Augustus  III., 

1813-26 

214 

833 

48 

Quarter-specie  thaler  of  Fred.  Augustus  III. 

1800-02 

107 

838 

24  2 

Sixth-specie  thaler  of  Fred.  Augustus  III., 

1803-10 

83 

537 

12 

New  thaler  of  Frederick  Augustus  IV., 

1839 

344 

750 

69  5 

Spain. 

Cob  dollar  of  Philip  V.  &  Charles  III.  Amer. 

1736-70 

410 

915* 

1  01 

Dollar  of  Philip  V.  &  Charles  III.,  Spanish, 

1731-32 

410 

910 

1  00  6 

Globe  dollar  of  Philip  V.  &  Charles  III. ,  A  mer. 

1736-71 

411 

910 

1  00  8 

Dollar  of  Charles  III.,  Spanish, 

1772-88 

412 

900 

99  8 

"      of  Ferdinand  VII.,  Spanish, 

1808-21 

414 

900 

1  00  4 

Pillar  dollar  of  Charles  III.  &  IV.,  Amer.,  1 

772-1808 

413 

8981 

99  8 

"            of  Ferdinand  VII.,  American,  J 

1808-25 

414 

898 

1  00  1 

Pistareen  of  Charles  the  Pretender, 

1707-12 

70 

900 

17 

of  Philip  v., 

1715-37 

81 

833 

18  2 

«'        of  Charles  III., 

1759-71 

85 

826 

18  9 

1772-1808 

85 

813 

18  6 

"        of  Isabella  II., 

1835-37 

90.5 

810 

19  7 

Five  pesetas  of  Barcelona  coinage. 

1809-11 

404 

890 

97  5 

Ten  reals  of  Resdlado, 

1821 

208 

920 

51  5 

Sweden. 

Specie  daler  of  Gustavus  III.  and  IV.,         1 

771-1801 

449 

880 

1  06  5 

of  Charles  John  XIV., 

1830-38 

525 

751 

1  06  2 

^  specie  daler  of  Gustavus  III., 

1784 

147 

875 

34  6 

1  specie  daler  of  Gustavus  IV., 

1803-07 

95 

686 

17  6 

Switzerland. 

Ecu  of  Zurich, 

1790-94 

390 

844 

88  7 

"    of  forty  batzen  of  Berne, 

1795-98 

452 

903 

1  10 

"    of  three  livres  (Genevoise)  of  Geneva, 

1796 

464 

868 

1  08  5 

Franken  of  Berne, 

1797 

122 

833 

27  4 

Four  franken  of  Helvetian  Republic, 

1801 

452 

900 

I  09  6 

Ten  batzen  of  Lucerne, 

1812 

110 

904 

26  8 

"           of  Vaud, 

1823 

112 

900 

27  1 

Five  batzen  of  Berne, 

1826 

67 

760 

13 

of  Vaud, 

1813 

63 

666 

11  3 

Thaler  of  Basle, 

1763 

356 

833 

80 

Crown  of  Basle, 

1795 

412 

840 

93  3 

Tripoli. 

Ghersh  of  100  paras  of  Mahmoud  II., 

188 

354 

17  9 

"                 "          of  Youssouf  Pasha, 

153 

244 

10 

Half-ghersh  of  100  paras  of  Mahmoud  II., 

98 

306 

8  1 

"                   "          of  Youssouf  Pasha 

, 

78 

241 

5  1 

Utchlik  of  Nedgib  Pasha, 

227 

245 

15 

*  Varies  from  913  to  922.  j  Varies  from  897  to  903. 

X  .Aiter  1S21  they  were  struck  at  Madrid     The  fineness  sometimes  is  as  high  as  905. 


SILVER. 

Table  of  Silver  Coins — Continued. 


855 


Nation. 

Weight. 

Fineness. 

Value. 

Grains. 

Thous. 

(1.    c.  m. 

Tunis. 

Piastre  of  Abchil  Hamed,  Sultan, 

238 

408 

26   1 

"       of  Mahmoud  II., 

176 

263 

12  8 

Double  piastre  of  Mahmoud  11., 

358 

270 

26 

TUKKET. 

Gliersh,  or  piastre,  of  Abdul  Hamid, 

1773 

294 

500 

39  G 

<i                        a                               a 

1783 

284 

550 

42  1 

"                 "         ofSelimllL, 

1794-1801 

200 

486 

26  2 

"                 "         of  Mahmoud  II., 

1823 

94 

470 

11  9 

Altmicklik,  1  J-  piastre,  of  Abdul  Hamid, 

178-i 

410 

550 

60  7 

Para  of  Selim-III., 

1794 

5 

500 

7 

"    of  Abdul  Medjid, 

1840 

2 

77 

i 

Tuscany. 

Francescone  of  Francis  III., 

1740-05 

419 

920 

1  03  8 

Ilalf-francescone  of  Francis  III., 

1740-G5 

199 

918 

49 

Ten  pauls  of  Ferdinand  III., 

1791-1801 

419 

920 

1  03  8 

11                              a 

1803-07 

420 

917 

1  03  7 

a                              ft 

1814-24 

421 

920 

I  04  3 

Ten  livres  of  Charles  I.  and  Maria  Louisa, 

1803-07 

607 

962 

I  57  3 

United  States. 

Dollar, 

1792-1837 

416 

892.4 

99  9 

1837  and  seq. 

412J 

900 

1  00 

The  silver  coinage  of  the  present  year  (1853)  is  de- 

based in  order  to  bring  it  down  to  a  standard  -whicli 

■will  prevent  it  from  leaving  the  country, 

and  which 

will  meet  the  rise  in  price  of  this  metal,  resulting 

from  the  changed  relations  between  it 

and  gold, 

which  have  arisen  from  the  increased 

quantity  of 

the  latter  recently  thrown  into  the  market.* 

WURTEMBERG. 

Convention  thaler  of  Charles, 

1760-84 

428 

836 

96  4 

"               of  Frederick, 

180G 

430 

833 

96  5 

Crown  of  William, 

1818-33 

454 

875 

1  07 

Gulden  of  William, 

1824 

195 

750 

39  4 

In  the  above  table,  as  well  as  in  that  of  gold  coins,  the  frac- 
tions of  coins  are  not  contained  when  they  are  of  the  same 
fineness  as  the  units.  So,  too,  slight  deviations  in  weight  in 
the  same  coin  are  not  taken  into  account  when  the  fineness 
remains  unchanged. 

Silver  plate  is  a  variable  alloy.  That  of  England  is  stamped, 
and  has  a  uniform  fineness  of  925  thousandths.     The  stamp  is 

*  The  three  cent  piece  contains  3  parts  of  silver  to  2  of  copper. 


356     CHEMISTEY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

a  lion,  with  the  initials  of  the  maker's  name,  the  seal  of  the 
assay  office  at  which  the  plate  was  examined,  and  a  letter  for 
the  date.  The  mark  of  the  goldsmith's  office  is  a  leopard's 
head  ;  the  office  at  Dublin,  a  harp  ;  at  Edinburgh,  a  thistle  ;  at 
Sheffield,  a  crown ;  at  Birmingham,  an  anchor ;  at  Newcastle, 
three  castles.  The  letter,  used  by  the  Goldsmiths'  Company, 
shows  the  date  by  beginning  the  alphabet  at  1817.  In  France 
there  are  two  standards,  950  and  800  thousandths.  The  Aus- 
trian standard  is  900.  Prussia  has  no  standard,  but  the  Corpo- 
ration of  Goldsmiths  controls  the  manufacture  of  plate,  so  as  to 
bring  it  to  750.  The  Mexican  rate  is  917,  though  it  is  not 
compulsory.  In  the  United  States  there  is  no  law  establishing 
the  quality  of  plate.  It  is,  however,  usually  that  of  our  coin, 
from  which  most  of  it  is  manufactured. 


SALTS  OF  SILVER. 
HALOID  SALTS. 

Chloride  of  Silver,  AgC\.  143.42. — This  substance,  which  occurs 
native  as  Jiorn  silver,  contains  75.38  per  cent,  of  silver,  and  is 
formed,  as  already  described,  by  adding  hydrochloric  acid,  or 
any  soluble  chloride,  to  a  solution  of  the  metal.  A  white,  curdy 
precipitate  falls,  which  is  to  be  washed  and  dried  away  from  the 
light.  Heated  to  dull  redness,  it  fuses  to  a  clear  yellow  liquid, 
which  is  converted,  on  cooling,  into  a  semitransparent,  gray,  or 
colorless  solid,  so  soft  as  to  receive  an  impression  from  the  nail. 

Fusion  with  potassa,  or  a  stream  of  hydrogen,  as  already 
described,  reduces  it  to  a  metallic  state.  Mohr  says  the  best 
way  of  reducing  it  is  to  mix  it  with  one-third  its  weight  of  colo- 
phony (black  rosin),  and  to  heat,  the  mixture  moderately  in  a 
crucible,  till  the  flame  ceases  to  be  of  a  greenish-blue  color; 
then  suddenly  to  increase  the  fire  so  as  to  melt  the  metal  into 
an  ingot.  Zinc,  tin,  cadmium,  bismuth,  copper,  lead,  mercury, 
arsenic,  and  antimony  reduce  it  under  water.  It  is  not  decom- 
posed at  a  red  heat,  even  when  mixed  with  calcined  charcoal ; 
but  hydrogen  or  steam,  passed  over  the  fused  chloride,  drives  off 
chlorine  as  hydrochloric  acid,  and  leaves  metallic  silver. 


SALTS  OF  SILVER.  357 

Alkaline  solutions  do  not  decompose  it,  but  it  forms  double 
salts  with  the  alkaline  chlorides  by  boiling  them  together,  and 
the  compound  salt  separates  in  crystals  on  cooling.  A  new 
method  of  obtaining  silver  from  its  ores,  based  upon  this  pro- 
perty of  its  chloride,  has  been  suggested.  The  ore  is  roasted 
with  common  salt  to  form  chloride  of  silver,  which  is  dissolved 
out  by  means  of  a  hot  solution  of  salt.  The  silver  is  precipi- 
tated by  metallic  copper.  Cyanide  of  potassium  also  dis- 
solves it,  and  it  crystallizes  out  of  the  solution,  on  evaporation. 
It  is  insoluble  in  water,  very  soluble  in  water  of  ammonia,  crys- 
tallizing out  of  its  solution. 

Suhcliloride  of  Silver,  Ag2Cl. — When  the  last  described  com- 
pound of  silver  is  placed  in  the  direct  rays  of  the  sun,  under 
water,  hydrochloric  acid  is  evolved,  and  the  precipitate  clianges 
to  a  blue-black.  The  same  result  takes  place,  but  with  less 
rapidity,  when  the  diffused  light  of  a  room  is  allowed  to  act 
upon  the  precipitated  chloride.  Berthollet  regarded  this  color 
as  due  to  the  formation  of  the  oxide  of  silver.  It  is  now  gene- 
rally conceded,  however,  that  a  new  and  definite  compound  of 
chlorine  and  silver  has  been  formed.  The  same  substance  may 
be  obtained  by  pouring  a  solution  of  deuto-chloride  of  copper  or 
perchloride  of  iron  upon  silver  leaf.  The  metal  is  speedily 
altered  to  black  spangles,  which,  being  quickly  washed  and 
dried,  constitute  the  subchloride  of  silver.  Should  the  solution 
remain  too  long  in  contact  with  the  silver,  the  chloride  will  be 
formed.  Hydrochloric  acid,  acting  on  suboxide  of  silver,  gives 
rise  to  the  same  compound.  It  is  a  brownish  or  black  powder, 
with  metallic  streak,  which,  when  heated  to  the  fusing  point  of 
chloride,  is  converted  into  chloride  and  metallic  silver. 

Bromide  of  Silver,  AgBr.  186.7. — This  is  formed,  like  the 
chloride,  by  double  decomposition  of  a  salt  of  silver  with  a  solu- 
ble bromide.  It  is  yellow,  fusible  to  a  red  liquid,  which  con- 
geals to  a  translucent  soft  mass.  It  is  only  slightly  soluble  in 
dilute  ammonia.  When  disseminated  in  water,  it  is  easily  decom- 
posed by  chlorine.  It  forms  double  salts  with  the  alkaline 
bromides. 

Iodide  of  Silver,  Agl.  234.6. — Formed  like  the  last  two 
salts,  substituting  a  soluble  iodide.     It  is  of  a  greenish  yellow 


358      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

color ;  fuses  to  a  red  liquid,  "which  congeals  to  a  dirty  yellow, 
opaque  mass  ;  is  readily  decomposed  by  chlorine  -when  heated  ; 
is  soluble  in  strong  solutions  of  iodide  of  potassium,  and  chloride 
of  potassium  or  sodium  ;  is  scarcely  soluble  in  ammonia.  It  forms 
double  salts  "with  alkaline  iodides,  "with  cyanide  of  potassium  and 
•with  basic  nitrate  of  mercury,  forming  "with  the  last  the  com- 
pound Agl+  Hgo,  No,+HO. 

Iodide  of  silver  possesses,  in  common  "with  other  metallic  salts, 
the  remarkable  property  of  changing  its  color  "with  variations  of 
temperature.  If  a  sheet  of  white  paper  be  "washed  over  "with 
a  solution  of  nitrate  of  silver,  and  afterwards  "with  iodide  of  po- 
tassium, it  immediately  assumes  the  pale  primrose  yellow  tint  of 
the  cold  iodide  of  silver.  On  gently  heating  the  paper,  the 
gaudy  brilliance  of  the  sunflower  takes  the  place  of  the  paler 
yellow,  into  "which  it  gradually  fades  as  the  paper  cools.  These 
changes  may  be  continued  indefinitely,  provided  too  high  a  heat 
be  avoided.  Pressing  the  finger  upon  the  warm  paper  produces 
a  "white  spot,  by  suddenly  cooling  the  part  "vvith  "which  it  comes 
in  contact. 

Fluoride  of  Silver,  AgFl.  127.05. — This  soluble  salt  is  formed 
by  the  action  of  hydrofluoric  acid  on  carbonate  of  silver.  When 
dry,  it  is  fusible,  like  the  chloride. 

Silico-fluoride  (3AgF  +  2SiF3)  is  soluble  and  crystallizable, 
and  is  precipitated  as  a  basic  salt  by  ammonia. 

OXYSALTS. 

Sulphate  of  Silver,  AgO,S03.  156.4. — Sulphate  of  silver 
may  be  prepared  by  the  action  of  boiling  sulphuric  acid  on  the 
metal,  as  described  under  the  head  of  parting  gold  and  silver  by 
means  of  this  acid.  It  may  also  be  procured  by  dissolving  the 
oxide  or  carbonate  in  dilute  oil  of  vitriol.  It  is  soluble  in  nitric 
acid,  from  "which  solution  it  crystallizes  in  white  shining  crys- 
tals ;  is  isomorphic  with  dry  sulphate  of  soda.  It  is  dissolved  in 
88  parts  of  boiling  water,  but,  on  cooling,  the  greater  part  falls 
down  in  acicular  crystals.  Dissolved  in  ammonia,  it  crystallizes 
out  as  AgO,S03+2NH3.  Nitric  acid  converts  sulphuret  of  sil- 
ver into  a  brownish-yellow  oxysulphate  or  sulphobasic  sulphate 
of  silver. 


SALTS  OF  SILVER.  359 

SulpJiite  of  Silver,  AgOjSOg.  148.4. — This  salt  is  precipi- 
tated from  a  solution  of  nitrate  of  silver  by  sulphuric  acid  or  a 
sulphite.  Hyposulphate  or  dithionate  of  silver  (AgO,S203+ 
2Ho),  is  obtained  from  a  solution  of  carbonate  of  silver  in  di- 
thionic  acid. 

Hyposulphite  of  Silver. — Dithionite  of  silver,  AgOjSjOj. 
172.5.  When  moderately  dilute  nitrate  of  silver  is  added  to  a 
concentrated  alkaline  dithionite  in  excess,  a  gray  precipitate 
falls,  ■svhich  is  a  mixture  of  dithionite  and  sulphate  of  silver. 
This  is  to  be  well  washed  with  pure  water  and  digested  with  am- 
monia, which  dissolves  the  dithionite  of  silver.  It  is  precipitated 
from  its  ammoniacal  solution  by  the  careful  addition  of  nitric 
acid  to  exact  neutralization.  It  is  filtered,  and  dried  rapidly  in 
paper.  This  salt  forms  double  salts  with  other  dithionites. 
These  are  made  by  saturating  a  solution  of  an  alkaline  dithionite 
with  chloride  of  silver,  and  precipitating  by  alcohol.  The  pre- 
cipitate is  to  be  dried  in  vacuo,  over  oil  of  vitriol.  Oxide  of 
silver  has  so  powerful  an  affinity  for  dithionous  acid  that  it 
abstracts  half  of  it  from  alkaline  dithionites,  making  a  strongly 
alkaline  solution.  The  alkaline  double  salts  are  crystalline  ; 
those  of  strontia,  lime,  and  lead  are  white  powders.  They  are 
all  characterized  by  intense  sweetness.  The  double  hyposulphite 
of  silver  and  ammonia  is  said  to  be  so  extremely  sweet  as  to  com- 
municate a  sensation  of  pain  to  the  tongue,  and  to  impart  a 
sweet  taste  to  32,000  parts  of  water.  Trithionate  and  tetra- 
thionate  of  silver  are  whitish  and  yellow. 

Nitrate  of  Silver,  AgO,N03. — This  salt  is  formed  directly  by 
the  union  of  pure  silver  with  pure  nitric  acid  ;  more  conveniently, 
however,  by  acting  upon  silver  coin  with  the  same  acid.  A  few 
insoluble  dark  flocks  are  left  after  the  action  of  the  acid.  These 
are  minute  portions  of  gold,  contained  in  nearly  all  silver  coin, 
and  are  to  be  separated  by  filtration.  The  filtered  liquid  has  a 
pale  blue  tint,  owing  to  the  presence  of  nitrate  of  copper.  This 
salt  is  separated  by  two  different  methods  from  the  nitrate  of 
silver.  One  of  these  is  the  evaporation  of  the  solution  to  dry- 
ness and  the  fusion  of  the  resulting  salt  in  a  platinum  capsule, 
till  all  green  tint  disappears  from  the  salt,  or  better,  till  a  por- 
tion of  it,  taken  out  and  dissolved  in  water,  gives  no  red  precipitate 


360     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

■R-itli  ferrocyanicle  of  potassium.  This  process  depends  upon  the 
ready  decomposition  of  nitrate  of  copper  bj  heat,  and  its  reduction 
to  oxide  of  copper.  This  being  insoluble  in  water,  the  desired  salt 
is  easily  obtained  pure  by  solution  in  water  and  crystallization. 
Another  method  is  to  precipitate  the  mixed  nitrates  by  hydro- 
chloric acid,  to  reduce  the  chloride  of  silver  by  zinc,  as  already 
directed,  to  redissolve  in  dilute  nitric  acid,  and  to  crystallize 
from  this  solution,  or  to  fuse  it  and  cast  it  in  cylinders.  In  the 
latter  form,  it  is  called  lapis  infernalis,  or  lunar  caustic,  and  is 
used  largely  by  surgeons  as  an  escharotic,  styptic,  and  local 
alterative. 

The  crystals  belong  to  the  right  rhombic  system.  They  are 
colorless  and  transparent,  and  do  not  deliquesce  by  exposure  to 
the  air.  They  contain  no  water  of  crystallization,  and  fuse 
readily  to  a  clear  liquid,  which  congeals  to  a  fibrous  solid  without 
loss  of  weight.  This  salt  destroys  organic  matter,  leaving  a 
white  pellicle,  which  turns  to  a  black  crust.  The  pure  salt  is 
soluble  in  its  own  weight  of  cold,  half  its  weight  of  hot  water, 
and  in  four  times  its  weight  of  hot  alcohol.  The  aqueous  solu- 
tion in  a  glass  bottle  undergoes  no  change  even  in  sunlight ;  but 
when  exposed  to  light,  especially  to  the  direct  rays  of  the  sun, 
in  contact  with  paper,  or  any  organic  substance,  a  black  stain 
is  quickly  produced,  owing  to  the  decomposition  of  the  salt  and 
reduction  of  its  oxide.  This  reaction  is  so  constant  and  so 
prompt  that  it  is  a  most  delicate  test  for  the  presence  of  organic 
matter,  and  used  in  medico-legal  examinations  for  the  removal 
of  this  disturbing  element  from  solutions  containing  some  of  the 
metallic  poisons.  It  deflagrates  on  redhot  coals ;  and,  when 
mixed  with  phosphorus,  explodes  at  a  blow.  At  low  redness  it 
is  decomposed  into  silver,  oxygen,  nitrogen,  and  nitric  oxide. 

To  the  analytical  chemist,  nitrate  of  silver  is  an  invaluable 
reagent,  being  applied  to  the  detection  of  a  variety  of  substances. 
By  the  housewife  it  is  used  for  marking  linen,  under  the  name 
of  indelible  ink.  The  barber  makes  a  solution  of  it  for  the  pur- 
pose of  blackening  hair  of  various  light  tints,  which  he  accom- 
plishes by  washing  the  hair  with  it  and  exposing  it  to  light  or 
the  action  of  some  soluble  sulphuret. 

There  are  a  number  of  double  nitrates.    The  ammonio-nitrate 


SALTS  OF  SILVER.  361 

(AgO,N05  4-2NH3)  crystallizes  from  a  solution  of  the  simple 
nitrate  in  ammonia.  It  darkens  readily  in  the  light.  It  is  one 
of  the  liquid  tests  for  arsenic,  with  which  it  gives  a  pale-yellow 
precipitate.  The  double  salt  with  mercury  {AgO,N03+  HgONO.) 
is  crystallizable.  There  are  also  double  salts  with  the  cyanides 
of  copper,  silver,  and  mercury. 

Nitrite  of  Silver,  AgO,]Sr03. 156.3. — When  a  solution  of  nitrite 
of  soda  is  poured  into  a  solution  of  nitrate  of  silver,  a  precipi- 
tate subsides,  which  is  soluble  in  hot  water,  from  which  it  crys- 
tallizes. This  nitrite  of  silver  is  white,  soluble  in  120  parts  of 
water  at  59°.  It  may  be  used  to  prepare  other  metallic  nitrites 
by  adding  it  to  the  chlorides. 

The  basic  salt  is  formed  by  boiling  silver  with  nitrate  of  silver, 
and  evaporating  the  yellow  solution  till  it  thickens  on  cooling  to 
a  crystalline  mass.  Water  decomposes  it  into  a  neutral  and 
more  basic  salt,  which  separates  as  a  yellow  powder. 

Phosphate  of  Silver,  oAgOPO^.  187.7.— When  a  solution  of 
the  common  phosphate  of  soda  is  dropped  into  a  neutral  solution 
of  nitrate  of  silver,  a  lemon-yellow  powdei',  the  phosphate  or 
triphosphate  of  silver,  subsides.  It  is  soluble  in  acids  or  ammo- 
nia, subsiding  from  the  latter  in  crystalline  grains.  It  must 
be  dried  away  from  the  light,  for,  like  other  salts  of  silver,  it 
blackens  when  exposed.  Its  color  changes  to  reddish  brown  on 
the  application  of  heat,  but,  on  cooling,  returns  to  its  original 
color  again.     It  fuses  at  a  white  heat. 

The  neutral  phosphate  is  made  by  dissolving  the  basic  salt  in 
warm,  concentrated  phosphoric  acid,  or  by  adding  excess  of 
phosphoric  acid  to  nitrate  of  silver  and  evaporating.  It  forms 
large  colorless  crystals,  which  are  decomposed  by  water,  leaving 
the  yellow  basic  salt. 

The  neutral  j^hosj^hate  of  the  bibasic  acid,  the  dipyrophos- 
phate  of  oxide  of  silver  (2AgO,P05)  is  obtained  by  adding  dipyro- 
phosphate  of  soda  to  nitrate  of  silver.  It  falls  as  a  snow-white 
granular  precipitate,  which  fuses  at  a  heat  below  incandescence 
into  a  dark-brown  liquid,  becoming,  on  cooling,  a  crystalline 
enamel.  The  biphosphate  of  the  same  group  (AgOPO^)  is  pre- 
cipitated from  nitrate  of  silver  by  an  ice-cold  solution  of  freshly 
ignited  bibasic  phosphoric  acid.     It  is  white,  very  fusible  at  a 


862   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

temperature  a  little  above  the  boiling  point  of  water.  It  loses 
acid  by  washing,  and  if  heated  gradually  in  water  to  212°,  it 
forms  a  sesquiphosphate  (3  AgO,2P05). 

Perehlorate  of  Silver,  AgOjClO^.  207.78. — This  salt  is  made 
by  the  direct  action  of  perchloric  acid  on  oxide  of  silver.  It  is 
a  white  powder,  deliquescent  and  soluble  in  alcohol.  It  melts 
and  explodes  at  a  heat  below  redness. 

Chlorate  of  Silver,  AgO,C105. 191.78.— This  salt,  like  the  last, 
is  made  by  the  direct  union  of  its  component  parts.  It  crystal- 
lizes in  four-sided  prisms,  which  are  soluble  in  5  parts  of  cold 
and  2  parts  of  hot  water,  and  slightly  in  alcohol.  It  is  more 
explosive  than  the  alkaline  chlorates,  and  is  decomposed  by  acids 
into  oxygen  and  chloride  of  silver.  When  am?iionia  is  added  in 
excess  to  its  solution  and  evaporated,  crystals  of  ammonio-chlo- 
rate  of  the  form  AgO,C105-f2NH3,  separate. 

Chlorite  of  Silver,  AgOjClOj.  175.78.— This  salt  occurs  in 
yellow  crystalline  scales,  and  is  formed  by  precipitating  nitrate 
of  silver  with  an  alkaline  chlorite,  boiling  the  precipitate  with 
water,  filtering  hot  and  crystallizing.     It  explodes  at  22 L°. 

Basic  Periodate  of  Silver,  2AgO,I07+3HO. — Basic  perio- 
date  of  soda  throws  down,  from  a  solution  of  nitrate  of  silver,  a 
precipitate,  which  dissolves  in  warm  nitric  acid,  and  separates,  on 
cooling,  in  shining  straw-yellow  crystals.  It  is  the  basic  perio- 
date of  silver,  which  loses  its  water  of  crystallization  on  being 
treated  with  warm  water,  and  is  converted  into  a  red  salt  of  the 
formula  3AgO,IO,-f  HO.  The  salt  AgOIO^,  in  yellow  crystals, 
decomposed  by  water  into  the  basic  salts,  separates  when  the 
solution  in  nitric  acid  is  evaporated. 

lodate  of  Silver,  AgOIOj. — This  salt  is  precipitated  when  an 
iodate  of  an  alkali  is  added  to  nitrate  of  silver.  It  is  white, 
and  soluble  in  ammonia. 

Carbonate  of  Silver,  AgO,C02.  138.3. — This  salt  precipitates 
from  a  solution  of  silver,  on  the  addition  of  an  alkaline  carbon- 
ate. It  is  yellowish,  slightly  soluble  in  water.  A  white 
aramonio-carbonate  is  obtained  by  precipitating  its  ammoniacal 
solution  with  alcohol. 

Borate  of  Silver,  AgOjBOg.  151.1. — A  white,  fusible,  slightly 


COPPEK.  363 

soluble  salt,  precipitated  when  a  concentrated  solution  of  borax 
is  mixed  with  a  solution  of  nitrate  of  silver. 

Chromate  of  Silver. — A  soluble  chromate  added  to  a  solution 
throws  down  a  crimson  chromate  of  the  metal.  If  precipitated 
from  acid  solutions,  a  bichromate  is  formed,  which  may  be 
obtained  by  direct  action  on  silver  in  fine  tabular  crystals  of  a 
rich  crimson.  The  bichromate,  when  boiled  in  distilled  water, 
falls  down  in  micaceous  crystals,  and  is  partly  decomposed  into 
chromic  acid  and  the  neutral  chromate,  which,  thus  prepared, 
is  green  by  reflected  and  crimson  by  transmitted  light,  and  in 
powder. 

Triarseniate  of  Silver  (SAgOjAsjOj)  is  a  brick-red  powder, 
obtained  by  precipitating  nitrate  of  silver  with  an  arseniate  of 
soda.  It  may  retain  some  of  the  nitrate,  a  property  which  it 
shares  in  common  with  the  phosphate. 


CHAPTER   IV. 

COPPER. 

Copper  is  a  very  abundant  metal,  and  was  well  known  to  the 
ancients.  With  them,  indeed,  it  supplied  the  place  of  steel. 
The  tools  which  have  been  found  in  the  old  Egyptian  quarries 
are  made  of  hardened  copper.  The  weapons  of  the  most  ancient 
times  were  constructed,  as  Hesiod  informs  us,  of  brass,  iron 
not  being  yet  used  for  that  purpose.  The  shields,  helmets,  and 
swords  of  Homer's  heroes  were  formed  of  the  same  material. 
In  later  times,  when  iron  had  superseded  the  ancient  metal,  the 
same  name,  ;j;axx£vj,  originally  applied  to  the  armorer,  and  mean- 
ing a  worker  in  brass  or  bronze,  was  retained  as  the  appellation 
of  the  blacksmith  who  wrought  in  iron.  The  brass  of  the  an- 
cients, or  xo-'>^xvi,  a  name  derived  from  the  Arabic,  and  signifying 
anything  capable  of  being  polished,  was  not  the  compound  to 
which  we  apply  that  name,  but  a  sort  of  bronze,  or  alloy  of 
copper  and  tin.     Our  English  word  copper,  as  well  as  the  terms 


364      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

used  in  the  different  modern  languages  to  designate  this  metal, 
are  derived  from  the  Latin  cuprum,  which  itself  comes  from 
Cyprus  or  Kupros,  as  it  was  spelt  by  the  Greeks,  an  island  sacred 
to  Venus,  where  it  was  extensively  mined  and  smelted  in  very 
ancient  times.  The  alchemical  title  of  copper  was  Venus,  and 
the  symbol  of  the  planet  was  applied  to  the  metal. 

The  ores  of  copper  are  so  numerous  that  it  would  be  impos- 
sible in  this  place  to  give  anything  like  a  full  account  of  them. 
A  glance  at  a  few  of  the  more  prominent  and  important  of  these 
must  suffice. 

Native  cojjper  is  found  in  most  mines  of  the  metal,  and  in 
some  places  it  is  exceedingly  abundant.  It  is  occasionally  found 
crystallized  in  octahedra  and  allied  forms.  More  commonly, 
however,  it  occurs  in  strings,  and  dendritic  lumps,  imbedded  in 
various  stones,  and  in  great  masses  resting  on  the  surface  of  the 
earth.  Lake  Superior  is  a  well-known  locality  of  the  metal. 
The  mass  lying  in  front  of  the  War  Office,  at  Washington,  Avhich 
came  from  that  region,  is  supposed  to  weigh  nearly  a  ton. 
Much  of  the  copper  sent  to  the  Eastern  States  from  the  mines 
on  Lake  Superior  is  in  great  slabs,  often  over  an  inch  in  thick- 
ness. In  Virginia,  it  abounds  in  the  Epidotic  trap  of  the  Blue 
Ridge,  much  of  that  rock  being  minutely  penetrated  by  the 
metal,  its  exposed  surface  being  covered,  and  its  narrow 
crevices  filled  with  sheets  of  copper.  At  the  Manassas  Gap, 
regular  veins  of  igneous  rock  are  worked,  which  are  full  of 
native  copper  "and  the  oxides. 

Copper  pyritcB  is  one  of  the  most  valuable  and  abundant  of 
the  ores  of  this  metal.  It  occurs  in  crystals  belonging  to  the 
quadratic  system.  These  are  a  definite  compound.  Rose's 
analysis  of  them  gives  in  percentage,  sulphur,  35.87;  copper, 
34.40;  iron^  30.47  ;  gangue,  0.27,  with  a  gain  of  1.01.  Another 
analysis  by  the  same  hand  amounted  to  copper,  33.12;  iron, 
30;  sulphur,  36.52;  silica,  39,  with  an  excess  of  0.3.  Ber- 
thier  found  copper,  32.1;  iron,  31.5;  sulphur,  36.3;  loss,  0.1. 
The  crystals,  therefore,  are  disulphuret  of  copper  and  sesquisul- 
phuret  of  iron,  CugS-fH^Sj. 

The  amorphous  pyrites,  however,  is  by  no  means  a  definite 
compound.     It  is  an  uncertain  mixture  of  the  sulphurets  of 


COPPER.  365 

iron  and  copper,  running  into  iron  pyrites  at  one  end  of  the 
scale  and  vitreous  copper  at  the  other.  Generally  pyritous  ores 
grow  richer  as  they  are  more  deeply  worked,  the  surface  ores 
containing  a  larger  proportion  of  iron  than  those  which  lie 
deeper.  This  may  probably  be  accounted  for  on  the  same  prin- 
ciple with  the  well-known  phenomena  of  alloys.  The  heavier 
metal  separates  from  the  lighter,  so  that  the  sulphurets  arrange 
themselves  in  the  order  of  their  specific  gravity. 

Copper  pyrites  is  of  a  bright  brass  yellow  color,  opaque,  with 
a  conchoidal  and  uneven  fracture,  and  a  metallic  lustre.  It 
may  be  cut  Avith  a  knife,  those  ores  which  are  richest  in  copper 
yielding  most  readily.  Its  streak  and  powder  are  a  rich  blackish 
green  or  deep  olive,  shining  with  a  dim  yellow  lustre.  It  tar- 
nishes readily,  and  presents  the  most  beautiful  deep  blue  and 
iridescent  tints. 

Copper  glance,  or  vitreous  copper,  is  a  fine  lustrous  deep  gray 
ore,  with  a  rich  purple  and  greenish  tarnish.  It  crystallizes  in 
forms  belonging  to  the  right  rhombic  system.  Klaproth's 
analysis  of  it  is,  copper,  78,5;  sulphur,  19.6,  with  iron  and 
silica.  The  last  substances  being  accidental,  the  essential  com- 
ponents, arranged  in  a  percentage  order,  would  be  in  the  pro- 
portion of  80  to  20.     The  formula  is  CU2S. 

This  ore  is  one  of  the  most  commonly  worked  in  the  United 
States.  Beautiful  specimens  of  it  are  found  at  the  Bristol  jVIine 
in  Connecticut,  the  Central  Mine,  of  New  Jersey,  and  at  Pipe 
Creek,  in  Maryland.  In  many  of  the  States,  it  has  been  found 
in  sufficient  quantities  to  be  worked  to  advantage. 

The  other  copper  ores,  as  malachite  or  native  carbonate,  diop- 
tase,  the  oxides,  the  sulphate,  the  phosphate,  atacamite,  &c.  do 
not  constitute  beds  or  working  mines  of  themselves,  but  accom- 
pany the  other  ores.  These  rarer  minerals,  therefore,  cannot 
occupy  our  attention. 

METALLUKGIC   TREATMENT   OP   COPPER   ORES. 

The  principal  ores  of  copper  which  are  smelted  are  the  sul- 
phurets, mixed,  of  course,  with  the  silicates,  carbonates,  and 
other  ores.     The  operations  for  this  purpose  are  very  various, 


366      CHEMISTRY  OF  METALS  AXD  EARTHS  USED  BY  THE  DENTIST. 

and  too  numerous  and  complicated  for  particular  description  in  a 
work  like  this.  The  process  adopted  at  Swansea,  however,  as 
described  by  Mr.  Vivian,  one  of  the  largest  smelters  in  Wales, 
gives  such  an  insight  into  the  behavior  of  copper  during  reduc- 
tion, that  it  is  worthy  the  attention  of  every  student  of  chem- 
istry. 

The  British  ores  are  all  poor.  The  average  of  the  ore  of 
Anglesey  is  only  from  2  to  3  per  cent.,  that  of  the  Cornish  cop- 
per about  8.  The  ore  smelted  in  the  United  States,  however, 
will  generally  average  20  per  cent,  of  metal,  the  rich  ore  being 
sent  to  the  furnaces  in  much  larger  quantity  than  the  poor. 
Many  of  our  American  ores,  when  sent  from  the  mines,  are  as 
rich  as  the  metal  obtained  after  the  second  smelting  in  Swansea. 
Ores  from  the  Bristol  and  Central  mines  in  Connecticut  and 
New  Jersey  have  frequently  yielded  from  48  to  51  per  cent,  by 
the  dry  assay.  At  one  time,  the  smelters  in  Baltimore,  then 
the  chief  smelting  city  in  the  Union,  would  purchase  no  ores  that 
gave  a  lower  average  yield  than  12  per  cent. 

The  principles  upon  which  the  smelting  of  sulphuretted  copper 
ores  depends,  will  be  clearly  understood  by  a  brief  account  of  the 
common  dry  assay. 

The  ore  to  be  assayed  is  reduced  to  fine  powder,  and  intro- 
duced into  a  roasting  dish,  or  a  crucible  which  is  laid  obliquely 
in  a  furnace  in  such  a  manner  that  there  may  be  a  free  circula- 
tion of  air  over  the  surface  of  the  ore.  The  heat  is  at  first  very 
moderate,  to  avoid  the  agglomeration  of  the  fine  particles,  and 
the  ore  is  stirred  briskly  till  it  is  uniformly  heated  through. 
The  heat  is  gradually  increased  ;  blue  flames  of  sulphur  begin 
to  play  over  the  surface,  and  the  ore  becomes  redhot.  The 
stirring  is  kept  up  to  bring  every  grain  under  the  influence  of 
atmospheric  oxygen,  and  a  glass  rod  dipped  in  solution  of  am- 
monia is  occasionlly  held  over  the  crucible  to  ascertain  whether 
acid  fumes  are  still  given  ofi".  When  the  rod  moistened  with 
ammonia  no  longer  fumes  when  held  over  the  crucible,  the  ore 
may  be  regarded  as  oxidated.  All  the  sulphur,  however,  is 
not  driven  off.  There  remains  a  portion  of  it  combined  with  the 
oxidated  copper,  as  a  sulphate.  To  get  rid  of  this,  finely  pul- 
verized carbonate  of  ammonia  is  to  be  added  portionwise  to  the 
mass,  and  thoroughly  incorporated  by  assiduous  stirring.     This 


COPPER.  367 

decomposes  the  sulphate  of  copper,  and  the  volatile  sulphate  of 
ammonia  is  driven  off  in  vapor.  The  ore  is  thus  reduced  to  a  mix- 
ture of  oxides  of  copper  and  iron  with  gangue.  It  is  now  rub- 
bed up  with  black  flux,  a  little  borax  laid  on  top,  and  the  whole 
fused  till  a  clear,  smooth,  thin  slag  is  formed.  The  copper  will 
be  found  as  a  metallic  button  at  the  bottom  of  the  crucible. 

The  object  here  is  to  get  rid  of  the  sulphur,  and  then,  by 
fusion  at  a  moderate  heat  in  contact  with  carbon,  to  reduce  the 
oxide  of  copper  to  a  metallic  state,  at  the  same  time  that  the 
alkalies  of  the  flux  and  the  earths  and  oxides  of  the  ore  form 
a  fusible  thin  glass,  which  allows  the  heavy  metallic  globules  of 
copper  to  fall  through  it  in  a  shower  and  to  collect  at  the  bottom 
of  the  crucible. 

The  same  end  is  attained,  when  working  on  the  large  scale,  in 
a  different  manner.  At  many  of  the  furnaces  in  Swansea,  there 
are  eight  operations  before  the  crude  ore  is  reduced  to  refined 
copper.  The  first  of  these  is  the  calcination  of  the  ore,  pre- 
vious to  which  the  ores  are  mixed  in  accordance  with  their  re- 
spective richness  and  the  varying  nature  of  their  gangue.  The 
latter  is  essential,  because  the  different  earths  contained  in  such 
a  mixture  mutually  flux  one  another.  The  mixed  ore  is  intro- 
duced into  a  calcining  furnace,  and  gradually  heated  with  con- 
stant stirring.  Sulphur  and  arsenic  burn  off,  the  ore  crumbles 
finer,  the  surface  of  the  lumps  are  reduced  to  oxides,  but  the 
centres  remain  sulphurets.  The  ore  is  now  transferred  to  a 
smelting  furnace,  in  which  it  is  ordinarily  mixed  with  some  crude 
or  unroasted  ore,  with  the  richer  portions  of  the  slag  from 
the  same  furnace,  and  with  the  scoriga  of  more  advanced 
smeltings.  Here  it  is  brought  to  a  state  of  perfect  fusion.  The 
lighter  oxides,  the  earthy  matters,  and  the  old  slag  combine  in  a 
glass  of  greater  or  less  tenacity,  while  the  metal,  owing  to  its 
greater  specific  gravity,  sinks  down  upon  the  sole  of  the  furnace. 
Its  accumulated  slag  is  raked  03"  from  time  to  time,  and  fresh 
ore  added  till  the  coarse  metal  has  reached  the  proper  height. 
It  is  then  drawn  off  into  water,  and  coarsely  granulated ;  more 
ore  is  added,  the  process  going  on  continuously  day  and  night. 
The  scorice  or  slags  are  then  broken  up  and  picked  over  ;  those 
portions  of  them  which  contain  globules  of  metal  are  sent  back 
to  the  furnace.     In  Wales,  these  slags   are   worked  down  so 


3G8      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

closely  that  they  contain  only  the  half  of  one  per  cent,  of  cop- 
per. In  this  country,  however,  the  high  price  of  fuel  and  labor 
■will  not  allow  such  close  working.  One  and  a  half  per  cent,  of 
copper  in  slag  will  not  pay  for  reduction. 

The  coarse  metal  obtained  is  a  mixture  of  sulphurets  of  iron 
and  copper.  This  is  roasted  precisely  as  the  ore,  but  oxidation 
goes  on  with  more  rapidity,  because  the  earthy  matters  which 
screened  the  sulphurets  from  the  action  of  the  air,  have  been 
removed. 

The  fourth  operation  is  another  fusion.  To  the  calcined 
coarse  metal,  rich  slags  and  cobbing*  are  added,  and  the  smelting 
conducted  as  in  the  first  fusion.  The  metal  is  either  granulated 
or  drawn  off  in  pigs,  according  as  it  is  to  be  calcined  or  not. 
The  fifth  process  is  a  calcination  of  the  produce  of  the  second 
smelting.  The  sixth  operation  is  the  smelting  of  the  last  cal- 
cined metal.  This  is  black  or  coarse  copper ;  and  it  is  trans- 
ferred to  a  furnace,  where  it  is  first  roasted  and  then  smelted. 
The  result  of  this  operation  is  pig  copper  or  blistered  copper,  as 
it  is  sometimes  called.  It  is  a  mixture  of  metallic  copper  with 
oxide  and  a  little  sulphuret. 

The  eighth  process  is  that  of  refining  and  toughening.  This 
is  a  very  nice  and  delicate  operation,  requiring  great  skill  and 
experience  on  the  part  of  the  workman  who  undertakes  it.  The 
pig  copper  is  laid  on  the  sole  of  the  refining  furnace  and  allowed 
to  remain  at  a  low  heat  for  several  hours  that  a  sort  of  roasting 
process  may  go  on.  The  heat  is  gradually  raised  till  the  metal 
is  melted.  Its  surface  is  then  covered  with  charcoal  to  reduce 
the  oxide  combined  with  pure  copper  in  the  pig  metal,  the  few 
scoria?  which  have  formed  having  been  first  raked  off.  The  as- 
say is  now  taken  by  dipping  a  small  ladle  into  the  metal  and 
cutting  and  breaking  the  button,  to  see  the  condition  of  the  cop- 
per. It  is  dark-red  and  coarse  grained.  A  stick  of  green  wood 
is  then  thrust  into  the  metallic  bath  and  briskly  stirred  round. 
The  hydrogen  and  carbon  thus  obtained  combine  with  the  oxygen, 
and  so  reduce  the  metal  to  a  pure  state.  If  too  much  carbon  be 
present,  a  brittle  carbonate  is  formed,  which  must  be  reduced 

*  This  term  applies  to  old  mortar  and  fragments  of  brick,  &c.,  about  the 
furnaces,  which  have  become  saturated  with  various  compounds  of  copper. 


COPPER.  369 

by  atmospheric  air.  The  exact  point  is  attained  by  frequent 
assays  taken  in  the  manner  already  described.  When  the  cop- 
per is  in  the  proper  condition,  it  is  malleablcj  of  a  fine  red  color, 
and  its  fractured  surface  has  a  beautiful  silky  or  satin-like  lustre. 
The  refined  metal  is  cast  into  ingots  or  granulated. 

In  operating  upon  rich  ores,  these  processes  are  very  much 
modified.  There  is  no  calcination  requisite.  Much  sulphur  is 
necessary,  indeed,  in  order  to  prevent  the  slags  from  retaining 
too  much  copper,  for  the  globules  of  sulphuret  are  larger  and 
fall  more  readily  through  the  fluid  scoriae,  which  are  formed  in 
the  first  smelting,  and  which,  when  the  metal  below  them  is  too 
rich,  contain  innumerable  small  glittering  specks  of  copper. 
This  is  independent  of  the  fluidity  of  the  slag,  for  I  have  seen 
slags  as  smooth  as  bottle-glass  sparkling  all  over  with  these  little 
specks.  The  ores  are  therefore  directly  fused,  and  the  resulting 
red  metal,  as  it  is  called,  is  smelted  again  with  the  richer  slags. 
The  white  metal  proceeding  from  this  operation  is  again  smelted 
with  rich  slag  and  brought  to  the  condition  of  regulus,  the  mini- 
mum degree  of  sulphuration.  The  fourth  operation  is  the  re- 
duction of  this  regulus*  to  pig  copper,  which  is  subsequently 
refined  in  the  manner  already  described.* 

METALLURGIC   TREATMENT   OF   THE   ALLOYS   OF   COPPER. 

To  obtain  pure  copper  from  small  quantities  of  alloy,  recourse 
may  be  had  to  either  the  wet  or  the  dry  method.  The  latter 
process  is  called  refining. 

Refining  on  the  small  scale  is  exactly  analogous  to  cupella- 
tion ;  indeed,  it  is  a  cupellation  performed  on  copper.  Some 
copper  is  wasted  in  the  operation,  being  volatilized  or  carried 
into  the  cupel  with  the  litharge.  The  operation  is  conducted  in 
an  ordinary  cupelling  furnace,  but  the  temperature  being  neces- 
sarily high,  it  must  have  a  strong  draught.  The  phenomena  are 
very  much  the  same  as  those  already  described  under  the  head 

*  There  are  many  other  processes  which  have  been  adopted,  and  modifi- 
cations are  constantly  made  in  them ;  but  it  has  not  been  thought  necessary 
to  introduce  any  account  of  them  in  this  place. 
24 


370     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  Silver.  The  same  iridescent  pellicle  is  formed ;  the  same  rota- 
tion of  the  button  and  the  same  sudden  solidification  are  observed. 

In  the  large  way,  an  analogous  reduction  of  alloys  to  copper  has 
been  successfully  applied  to  bronzes  and  bell  metals.  Fourcroy  in- 
vented the  plan  during  the  wars  of  the  French  Revolution.  He 
oxidated  the  alloys  thoroughly  in  a  calcining  furnace,  and  then 
fused  a  quantity  of  unroasted  alloy  with  this  mixture  of  the 
oxides.  Metallic  copper  subsided,  and  scoriae,  composed  of  the 
oxides  of  tin  and  copper,  floated  on  the  surface  of  the  bath. 
The  scoriae  were  then  reduced,  and  the  metal  obtained  from 
them  treated  in  the  same  way  as  at  first.  When  they  were  very 
rich  in  tin,  the  alloy  obtained  from  them  was  skimmed  during 
the  oxidation,  and  thus  reduced  to  the  standard  of  bell  metal, 
because  the  tin,  oxidizing  more  readily  than  the  copper,  was 
found  in  greater  quantity  in  the  scoriae.  The  metal,  thus  pro- 
cured, was  treated  precisely  in  the  same  manner  as  at  first. 

The  process  of  eliquation  was  also  applied  to  the  same  pur- 
pose. The  blocks  of  metal  rich  in  tin  were  laid  on  the  sloping 
hearth  of  a  reverberatory  furnace,  and,  by  means  of  a  regulated 
heat,  the  more  fusible  metal  was  gradually  sweated  out. 

To  obtain  absolutely  pure  copper  from  the  alloys  of  this 
metal  by  the  humid  process,  the  common  method  is  to  dis- 
solve the  alloy  in  nitro-hydrochloric  acid,  to  evaporate  to  dry- 
ness with  frequent  moistening  with  hydrochloric  acid,  in  order 
to  drive  off  excess  of  nitric  acid,  and  then  to  boil  the  solution 
with  a  strip  of  metallic  zinc  or  iron  till  all  the  copper  is  precipi- 
tated, taking  care  to  have  the  solution  dilute  and  acidulous. 
When  zinc  is  employed,  the  copper  is  pasty  and  adherent,  and 
is  very  liable  to  oxidate  when  drying.  Iron,  however,  usually 
throws  down  the  metal  in  beautiful  minute  shining  scales.  Some- 
times it  precipitates  the  copper  in  thin  sheets  of  considerable 
tenacity,  smooth  and  shining  on  the  side  next  to  the  iron,  rough 
with  little  spangles  on  the  other  surface.  However  obtained,  it 
is  necessary  to  wash  the  precipitate  well,  first  with  dilute  sul- 
phuric or  hydrochloric  acid,  and  then  with  pure  water.  It  must 
be  dried  in  the  water-bath.     Too  high  a  heat  oxidates  it. 

Another  method  is  to  dissolve  the  alloy  in  the  usual  copper 
solvents,  filter  and  treat  the  solution  with  ammonia.  Potash, 
boiled  with  this  solution,  throws  down  the  black  oxide,  which  is  to 


1 


COPPER.  371 

be  sharply  dried,  then  introduced  into  a  gun-barrel,  or  better,  a 
porcelain  tube,  and  heated  to  redness,  while  a  stream  of  hydro- 
gen gas  passes  over  it. 


COPPER  AND   ITS   MORE   SALINE   COMPOUNDS. 

Copper  is  distinguished  from  all  metals,  except  titanium,  by 
its  color,  which  is  a  fine  brownish  red,  slightly  inclining  to  yel- 
low. It  is  susceptible  of  a  high  but  fugacious  polish,  as  it  is 
extremely  liable  to  tarnish.  It  is  soft  enough  to  be  cut  with  a 
knife,  though  more  resistant  than  lead.  Its  malleability  exceeds 
its  ductility,  so  that,  while  it  may  be  laminated  in  very  thin 
leaves,  it  cannot  be  drawn  out  to  extremely  fine  wire.  In  fine 
powder  it  welds  like  gold,  a  property  which  has  been  taken 
advantage  of  in  the  manufacture  of  medals.  Fine  copper  powder 
is  strongly  forced  into  the  die,  and  an  unusually  sharp  and  clear 
impression  is  thus  obtained.  The  medal  may  be  afterwards 
hardened  by  careful  annealing.  It  has  a  faint,  nauseous,  dis- 
agreeable taste  and  odor. 

The  specific  gravity  of  copper,  fused  in  the  open  air  (8.7  to 
8.8),  is  lower  than  the  average,  because  some  oxygen  is  absorbed 
from  the  atmosphere  and  the  metal  rendered  porous.  Fused 
under  a  protecting  slag,  its  sp.  gr.  is  8.91  to  8.921.  That  of 
the  unignited  wire  is  8.939  to  8.949  ;  of  the  ignited  wire,  8.93  ; 
of  flattened  wire  and  sheet,  8.95.  Its  fusing  point  is  1,996°, 
intermediate  between  that  of  silver  and  of  gold. 

At  a  high  temperature  it  is  volatile,  and  even  at  its  fusing 
point  a  considerable  quantity  of  it  escapes  into  the  atmosphere. 
In  the  most  carefully  managed  furnaces  this  loss  is  unavoidable, 
and  usually  amounts  to  the  fourth  of  one  per  cent.,  or  it  may 
go  much  higher  than  this.  In  a  properly  conducted  smelting 
establishment,  the  loss  ought  never  to  exceed  the  half  of  one  per 
cent.  All  the  ores  of  copper  are  volatile,  and  in  a  furnace 
without  a  culvert  much  metal  must  necessarily  be  lost.  The 
author  has  known  20  tons  of  fine,  impalpable,  reddish  dust, 
containing  on  an  average  14  per  cent,  of  copper,  to  be  taken 
out  of  the  culvert  of  a  smelting  establishment,  as  the  residuum 
of  about  3,000  tons  of  ore,  averaging  22  per  cent. 

Its  symbol  is  Cu ;  its  equivalent,  as  determined  from  the  re- 


372      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

duction  of  the  black  oxide  by  hydrogen,  is  31.71  on  the  hydrogen, 
and  396.7  on  the  oxygen  scale.  Some,  who  regard  the  black 
oxide  as  a  deutoxide,  make  it  63.42. 

Oxides. — When  copper  is  fused  in  the  atmosphere,  tarnishes 
of  various  hues  of  yellow,  red,  purple,  and  black,  form  on  its 
surface.  These  indicate  various  admixtures  of  the  two  oxides 
with  metal,  and  may  be  conveniently  seen  on  the  surface  of 
ingots  sent  to  market.  When  these  have  been  allowed  to  cool 
too  long  in  the  air  after  being  cast,  they  are  invariably  coated 
with  a  black  layer.  When  they  have  been  immersed  early  in 
the  water,  the  tarnish  is  either  an  orange  yellow  or  a  fine  ruby 
red,  or  a  mixture  of  these  two.  It  is  upon  the  proper  manage- 
ment of  this  that  the  preparation  of  Japan  copper  depends. 
This  is  cast  in  small  moulds,  and  the  moment  it  has  consolidated 
it  is  thrown  into  water,  where  it  becomes  covered  with  a  beauti- 
ful red  film  of  suboxide.  Heated  in  oxygen  or  the  flame  of  the 
compound  blowpipe,  copper  burns  with  a  rich  green  light,  and 
is  wholly  converted  into  black  oxide.  Its  tarnish,  gradually 
acquired  from  the  atmosphere,  is  at  first  a  warm  deep  brown, 
which  gradually  passes  into  the  dark  olive-green,  so  highly  prized 
by  antiquaries,  a  color  produced  by  the  mixture  of  the  carbonate 
and  the  two  oxides.  Acids  corrode  it  and  form  salts  with  it 
which  are  poisonous. 

Dioxide  of  Copper,  CujO.  71.42. — This  compound  occurs  na- 
tive, as  red  copper  ore.  It  has  been  found  amorphous,  and  in 
brilliant,  blood  red,  half-transparent  octahedral  crystals.  It  is 
often  found  melted  through  quartz  in  the  neighborhood  of  native 
copper,  giving  the  silicious  stone  a  beautiful  ruby  red  color. 

It  may  be  made  by  calcining  the  metal  in  a  muffle ;  or  by 
igniting,  in  a  covered  crucible,  a  mixture  of  31.71  parts  of  copper 
filings  with  39.71  of  black  oxide,  or  24  parts  of  anhydrous  blue 
viti'iol  and  29  parts  of  finely  divided  copper.  A  very  fine  metal- 
lic pigment  has  been  made  by  mixing  intimately  100  parts  of 
sulphate  of  copper  with  59  parts  of  carbonate  of  soda ;  fusing 
these  in  their  water  of  crystallization  at  a  low  temperature,  and 
continuing  the  heat  till  the  mixture  is  dry ;  then  mixing  inti- 
mately with  them  25  parts  of  finely  divided  metallic  copper,  and 
heating  the  whole  in  a  covered  crucible  to  whiteness  for  twenty 
minutes.     An  analogous  process  of  deoxidizing  the  black  oxide 


COPPER.  373 

is  heating  to  redness  in  a  carefully  closed  crucible  a  series  of 
alternate  strata  of  fine  copper  sheets  and  black  oxide  of  copper. 
The  dichloride  may  be  decomposed  by  carbonate  of  soda  in  a 
closed  crucible,  and  the  resulting  chloride  of  sodium  washed  out, 
leaving  the  dichloride  of  copper.  Or,  lastly,  a  solution  of  one 
of  the  salts  of  the  protoxide,  say  the  acetate,  may  be  boiled  -with 
sugar,  when  the  red  oxide  of  copper  falls  down.  Trommer's 
test  for  saccharine  urine  depends  on  this  reaction.  This  oxide 
is  always  formed  when  a  large  quantity  of  metallic  copper  is 
fused  under  scoriae  sufficiently  thin  to  admit  a  little  atmospheric 
air.  It  is  often  found  on  the  sides  of  refining  furnaces  mixed 
with  the  black  oxide,  and  then  the  mass  is  crystalline  in  its 
texture,  dark  gray  in  color,  with  metallic  lustre,  and  flecked 
with  magnificent  ruby-red,  semi-transparent  patches. 

This  compound  varies  in  color  from  a  brownish  copper  red  to 
a  pure  carmine  tint.  The  hydrated  suboxide  is  yellow.  In  a 
dry  atmosphere  it  may  be  kept  for  a  long  time,  but  moisture 
rapidly  peroxidates  it.  Heated  to  redness,  it  is  converted  into 
the  black  oxide.  The  acids  act  upon  it  variously.  Most  of 
them  decompose  it  into  a  salt  of  the  black  oxide  and  metallic 
copper.  Strong  nitric  acid  oxidates  it  with  the  evolution  of 
binoxide  of  nitrogen.  Hydrochloric  acid  dissolves  it,  forming  a 
colorless  solution,  from  which  the  alkalies  and  their  carbonates 
throw  down  yellow  or  red  precipitates,  and  ferrocyanide  and 
iodide  of  potassium  white  or  brownish  ones.  Ammonia  dissolves 
it  to  a  colorless  fluid,  which  rapidly  becomes  blue  from  absorption 
of  oxygen. 

Fused  with  glass,  this  oxide  forms  a  fine  rich  ruby-red  when 
proper  care  is  taken  to  prevent  oxidation.  A  little  metallic  tin 
is  often  mixed  with  it  for  this  purpose.  Its  coloring  power  is 
very  intense,  so  that  an  exceedingly  thin  film  may  be  blown  out 
as  a  coating  to  a  vessel  of  transparent  glass.  The  outer  film 
may  be  then  cut  through,  and  various  forms  obtained  in  colorless 
glass.  Pastes  are  also  colored  by  it  to  imitate  the  ruby  and  the 
garnet. 

Black  Oxide  of  Copper,  CuO.  39.71. — This  oxide  is  also  found 
native  as  copper-black,  in  amorphous  earthy  powder  or  lumps, 
and  sometimes  fused  in  the  cupriferous  trappean  rocks.  In  the 
latter  instance,  it  is  commonly  found  investing  the  native  copper. 


374      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

and  it  always  presents  a  brilliant  metallic  lustre.  Its  dark  rich 
gray  tint  causes  it  often  to  be  confounded  with  the  vitreous  ore 
of  Brochant,  or  the  Fahlerz  of  the  Germans ;  from  which,  how- 
ever, it  may  be  easily  distinguished  by  its  solubility  in  hydrochlo- 
ric acid  without  residue.  The  author  has  seen  this  oxide  sub- 
limed through  the  porous  bricks  of  a  refining  furnace,  and 
condensed  in  the  cavities  in  bright,  lead  gray  acicular  crystals. 

It  is  best  prepared  by  igniting  the  crystallized  nitrate  in  a 
platinum  crucible,  or  by  precipitating  the  blue  ammoniacal  solu- 
tion by  caustic  potassa  at  a  boiling  temperature.  Calcination 
of  the  metal  gives  a  mixture  of  the  oxides. 

The  color  varies  from  a  deep  brown  to  a  bluish-black.  The 
hydrated  oxide  is  blue  with  a  slight  cast  of  green.  Its  specific 
gravity  is  6.401.  At  a  high  temperature,  it  fuses  to  the  crys- 
talline mass  already  described.  Heated  to  redness  with  carbon 
or  hydrogen,  it  is  reduced  to  metallic  copper.  Deoxidating 
agents,  such  as  protoxide  of  iron,  protochloride  of  tin,  and  organic 
matters  at  a  boiling  temperature,  convert  it  into  dioxide.  Ver- 
diter  is  a  mixture  of  its  hydrate  and  carbonate.  Its  solution  in 
ammonia  is  blue. 

The  salts  of  this  oxide  are  numerous.  When  anhydrous,  they 
are  commonly  white ;  when  hydrated,  of  a  rich  blue  or  green 
tint.  From  their  solution,  iron  or  zinc  separates  metallic  copper, 
and  the  alkalies  the  greenish-blue  hydrated  oxide.  Ammonia 
in  small  quantity  throws  down  a  pale  bluish-green  subsalt,  and 
in  excess  dissolves  it  again,  forming  an  ultramarine  blue  solution. 
The  carbonates  throw  down  a  greenish-blue  precipitate,  which 
is  a  mixture  of  carbonate  and  hydrated  oxide.  It  is  precipitated 
white  by  iodide  of  potassium;  mahogany  brown  by  ferrocyanide 
of  potassium;  dark  brown  or  black  by  sulphuretted  hydrogen; 
brownish-yellow  by  ferridcyanide  of  potassium;  reddish-brown 
by  chromate  of  potassa ;  white,  with  a  shade  of  beryl  green,  by 
oxalic  acid.  A  clean  rod  of  iron  is  stained  with  a  solution  of 
copper,  containing  1  part  of  the  oxide  in  100,000.  Tincture  of 
guaiacum  gives  a  blue  tint,  changing  to  green  with  a  solution  con- 
taining 1  part  of  copper  salt  to  450,000  of  water.  Ferrocyanide 
of  potassium  will  give  a  mahogany  tint  to  651  gallons  of  water, 
holding  in  solution  a  grain  of  copper.  Albumen  throws  down 
an  insoluble  yellowish-white  precipitate,  which  has  been  proved 


COPPER.  375 

by  Orfila  to  be  inert;  so  that  albumen  may  be  used  as  an  anti- 
dote to  poisoning  by  copper. 

Peroxide  of  Qopper^  CuOj.  47.71. — Thenard  obtained  this 
compound  by  acting  on  the  hydrated  oxide  with  peroxide  of 
hydrogen.  It  undergoes  spontaneous  decomposition  under 
water,  but  may  be  dried  over  sulphuric  acid  in  vacuo. 

Cujyric  Acid. — When  nitrate  of  copper  is  added  to  a  solution 
of  bleaching  salt,  with  excess  of  lime,  at  a  temperature  below 
32°  F.,  the  bluish-green  precipitate  becomes  purplish-red.  It 
is  washed  with  cold  lime-water.     Its  formula  seems  to  be  CU2O3. 

tSuIphurets. — There  are  several  combinations  of  copper  and 
sulphur. 

Disulphuret  of  Copper,  CugS.  79.52. — Occurs  native  as 
copper  glance.  It  may  be  formed  artificially  by  heating  copper 
filings  with  finely  divided  sulphur,  and  by  acting  on  copper  foil 
by  vapor  of  sulphur. 

This  is  a  very  fusible  and  somewhat  volatile  compound. 
Ignited  in  atmospheric  air  or  oxygen  gas,  it  is  converted  into 
the  black  oxide,  sulphurous  acid,  and  sulphate  of  copper.  Fusion 
with  saltpetre  produces  oxide  of  copper  and  sulphate  of  potash; 
with  the  alkaline  carbonates  and  charcoal,  a  small  quantity  of 
metal  and  a  large  bead  of  regulus.  Ignition  with  oxide  of  cop- 
per expels  sulphurous  acid,  and  leaves  metal  or  suboxide. 

Sulphuret  of  Copper,  CuS.  47.81. — This  compound  is  found 
native  as  cop>per  indigo.  It  is  precipitated  when  a  salt  of 
copper  is  treated  with  sulphuretted  hydrogen.  Thus  obtained, 
it  is  brownish-black,  easily  oxidated,  converted  into  a  sulphate 
by  exposure  to  the  air,  by  roasting,  or  by  fusion  with  nitre. 

There  are  several  other  sulphurets  of  copper,  of  which  the 
proto-sulphuret  is  unchangeable  in  the  air  and  soluble  in  alka- 
line carbonates.  An  oxysulphuret,  according  to  Pelouze,  of  the 
former,  5CuS-f  CuO,  is  produced  when  a  sulphuret  in  solution 
is  poured  into  a  copper  salt. 

PhospJiurets. — Phosphuret  of  copper,  obtained  by  igniting 
copper  with  phosphorus,  or  phosphate  of  copper  with  charcoal, 
is  a  mixture  of  copper  of  different  degrees  of  phosphorization, 
fusible,  nearly  as  hard  as  steel,  brittle,  of  a  color  varying  from 
copper  red  to  steel  gray,  in  proportion  to  the  percentage  of 


376      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

phosphorus.  When  phosphuretted  hydrogen  is  passed  over 
phosphate  of  copper,  CU2P  is  obtained.  A  suhsulpliophospliite 
is  formed  when  bisulphuret  of  copper  is  treated  with  sulphur et 
of  phosphorus,  and  gently  warmed  in  a  current  of  hydrogen. 
It  is  a  yellow  powder,  of  the  composition  2CuS,PS3.  By 
heating  this,  two  equivalents  of  sulphur  are  driven  off,  leaving 
2Cu2S,PS. 

The  hi/jposulphophosphite  (CuS,PS)  is  obtained  like  the  last 
compound  by  using  the  sulphuret  of  copper  instead  of  the  bisul- 
phuret. Various  salts  are  formed  from  it  by  decomposing  it 
through  the  agency  of  heat. 

Nitruret  of  Copper. — Nascent  copper  at  a  high  temperature 
has  an  affinity  for  nitrogen,  and  forms  a  definite  compound  with 
it,  CugN.  It  is  a  greenish  powder,  obtained  by  passing  perfectly 
dry  ammoniacal  gas  over  oxide  of  copper  heated  in  a  glass  tube 
to  482°.  Nitrogen  and  water  are  also  produced,  and  the  decom- 
position is  attended  by  a  remarkable  rise  of  temperature.  At 
a  heat  of  572°,  the  compound  is  resolved  into  nitrogen  and 
metallic  copper. 

Hydrwet  of  Copper. — When  from  a  solution  of  10  parts 
hypophosphite  of  baryta  all  the  baryta  is  exactly  precipitated 
by  the  addition  of  sulphuric  acid,  and  8  parts  of  sulphate  of 
copper  are  then  introduced  into  it,  a  heat  of  158°  will  throw 
down  a  precipitate,  first  yellow  and  then  orange.  Should 
bubbles  of  hydrogen  escape,  the  vessel  must  be  cooled.  The 
deposit  is  to  be  collected  on  a  filter  and  washed  in  an  atmosphere 
of  carbonic  acid,  with  water  deprived  of  air.  It  is  then  to  be 
dried  between  folds  of  bibulous  paper.  Its  composition  is  sup- 
posed to  be  CujH. 

ALLOYS  OF  COPPER. 

Copper  unites  with  most  of  the  metals,  forming  many  alloys 
of  the  greatest  practical  value.  The  most  ancient  of  these  are 
the  compounds  of  copper  and  tin.  Antique  swords  were  made 
of  these  two  metals  in  varying  proportions.  A  sword  found  in 
the  peatmoss  of  the  Somme  contained  copper,  87.47;  tin,  12.53. 
Another,  found  near  Abbeville,  was  composed  of  85  copper  to 


COPPER.  377 

15  of  tin,  and  another,  of  90  of  copper  to  10  of  tin.  The 
bronze  springs  of  the  balistse  were  made  of  copper  97,  tin  3. 

The  application  of  bronze  to  the  casting  of  statues  had  its 
origin  in  a  very  remote  period.  It  was  not,  however,  brought 
to  anything  like  perfection  till  about  700  years  before  the 
Christian  era,  after  which  time  it  became  a  favorite  material  for 
statues.  To  this  purpose  it  is  well  adapted,  as  it  expands  in 
cooling,  and  is  thus  forced  up  into  all  the  little  inequalities  of 
the  mould,  giving  a  clear  sharp  outline  not  to  be  obtained  from 
any  other  material.  It  requires,  however,  much  skill  to  manage 
it  properly.  Besides  the  property  of  alloys,  already  alluded 
to,  to  separate  into  strata,  according  to  the  specific  gravities 
of  the  metals  composing  them,  the  varying  afiSnities  for  oxygen 
of  the  component  parts  of  bronze,  is  another  difficulty  in  the 
way  of  the  artisan.  The  column  of  the  Place  Vendome,  in 
Paris,  is  an  example  of  the  inability  of  the  artist  to  overcome 
this  obstacle.  The  bass-reliefs  of  the  pedestal  of  this  column  con- 
tain 94  per  cent,  of  copper,  those  of  the  shaft  much  more,  and 
those  of  the  capital  99.79.  The  founder,  therefore,  had  gone 
on  driving  off  his  tin  by  oxidation  till  there  was  scarcely  any 
of  it  left.  The  cannon  from  which  these  castings  were  made 
contained  89.36  per  cent,  of  copper,  and  10.04  of  tin,  the  rest 
being  made  of  other  metals.  The  ancient  bronzes  are  composed 
of  copper  and  tin  alone.  Many  of  the  modern  are  brass  with 
excess  of  copper,  or  a  mixture  of  brass,  lead,  and  tin.  Bronze 
for  medals  is  composed  of  from  8  to  12  parts  of  tin,  and  92  to 
88  of  copper.  Two  or  three  parts  of  zinc  give  it  a  finer  bronze 
tint. 

Bell  metal,  of  the  finest  quality,  should  be  composed  of  copper 
78,  tin  22,  but  the  founders  increase  their  profits  at  the  expense 
of  the  sonorous  properties  of  the  alloy,  by  adding  zinc  and  lead 
to  the  mixture.  Chinese  gongs  have  the  above-named  composi- 
tion, varying  to  81  of  copper  and  19  of  tin.  They  contain  no 
other  metal. 

Cannon  metal  is  composed  of  copper  90  or  91  and  tin  10  or  9. 

Speculum  metal,  very  white  and  brilliant,  is  composed  of  cop- 
per 66 J ,  tin  331.     Brass  and  arsenic  are  often  added  to  this. 

Copper  and  Arsenic  form  a  white  alloy,  sometimes  used  for 


878      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

thermometer  and  barometer  scales,  dials,  &c.  It  is  composed  of 
9  parts  of  copper  to  1  of  arsenic.  To  attain  this  proportion, 
however,  it  is  necessary  to  introduce  3|  parts  of  the  latter  metal 
before  fusion,  which  operation  is  conducted  under  salt,  in  a 
closed  crucible. 

G-erman  silver  is  composed  of  copper,  40.4 ;  nickel,  31.6  ; 
zinc,  25.4  ;  iron,  2.6.  This  is  the  genuine  German  silver,  but 
there  are  many  imitations  and  modifications  of  it  made  after  a 
great  variety  of  formulae. 

Brass  is  a  compound  of  copper  and  zinc,  in  varying  propor- 
tions. During  the  melting  of  the  two  metals  together,  a  con- 
siderable loss  of  the  zinc  takes  place  in  consequence  of  its  ready 
volatility  and  combustibility,  so  that  more  zinc  must  be  added 
than  the  alloy  is  desired  to  retain.  The  exact  determination  of  the 
extent  of  this  volatilization  is  a  matter  of  some  nicety,  and,  as  it 
depends  on  a  variety  of  circumstances,  such  as  the  temperature 
and  draught  of  the  furnaces,  the  mode  of  admixture  of  the  two 
metals,  &c.,  the  manufacture  of  good  brass  requires  not  a  little 
skill  and  experience  on  the  part  of  the  workman.  Common 
brass  is  a  very  irregular  and  carelessly  made  compound,  much 
contaminated  with  tin  and  lead  arising  from  the  solder.  Yellow 
metal,  or  sheathing  brass,  is  usually  rated  at  60  copper  and  40 
zinc,  the  object  of  the  manufacturer  being  to  introduce  as  much 
as  possible  of  the  cheaper  metal  without  injuring  the  mallea- 
bility of  the  compound.  Practically,  however,  its  composition 
is  variable,  though,  in  good  sheathing  metal,  it  always  approxi- 
mates these  proportions. 

The  finest  brass  consists  of  about  63  of  copper  to  32  of  zinc 
(ZnCUj),  to  which  about  2  parts  of  lead  are  added  when  the 
brass  is  to  be  turned.  Brass  for  hammering  consists  of  70  of 
copper  to  30  of  zinc.  Mannheim  gold  consists  of  75  copper  and 
25  zinc,  separately  melted  and  suddenly  incorporated  by  stir- 
ring. Prince's  metal,  Dutch  foil,  similor,  and  pinchbeck  are  of 
similar  composition.  Red  brass,  called  tombac  by  some,  is 
brass  with  excess  of  copper,  the  proportions  varying  from  2^ 
to  8  or  10  of  copper  to  1  of  zinc.  Mosaic  gold,  aurum  musivum, 
according  to  Parker  and  Hamilton's  patent,  consists  of  100  of 
copper  to  52  or  55  of  zinc.     Brass  solder  is  composed  of  equal 


COPPER.  379 

"weights  of  the  two  metals,  or  two  parts  of  brass  and  one  of  zinc 
melted  together,  to  which  a  little  tin  is  sometimes  added.  Cop- 
per is  sometimes  roasted  with  brass  bj  exposing  it  to  the  vapor 
of  zinc.  The  spurious  gold  wire  of  Lyons  is  made  in  this  man- 
ner. Copper  vessels  are  coated  with  brass  by  boiling  them  in  a 
solution  of  argol  and  zinc  amalgam  in  hydrochloric  acid. 

Brass  melts  at  1869°  Fahrenheit,  and  loses  a  considerable 
proportion  of  zinc.  At  white  heat  it  still  retains  16  per  cent,  of 
this  metal,  and,  even  after  a  protracted  fusion  at  this  high  tem- 
perature, 3  or  4  per  cent,  of  zinc  remains.  Zinc  can  be  driven 
off  entirely  by  a  carefully  conducted  calcination  in  the  open  air. 

Besides  the  numerous  uses  to  which  metallic  brass  is  applied, 
it  is  also  employed  by  the  workers  in  colored  glass  to  stain  their 
wares.  For  this  purpose  it  is  repeatedly  calcined  till  a  brown 
powder  is  obtained,  -which  makes  the  glass  intumesce  when  fused 
with  it.  It  communicates  various  tints  of  green,  passing  into 
turquoise.  A  chalcedony  red  or  yellowish  tinge  is  obtained 
from  a  vitrifiable  pigment,  made  by  stratifying  brass  and  sulphur 
in  a  crucible,  calcining  them  at  a  red  heat,  and  then  roasting 
the  resulting  powder  in  a  reverberatory  furnace. 

Copper  forms  alloys  with  molybdenum,  tungsten,  manganese, 
and  iron.  As  a  general  thing,  copper,  alloyed  with  iron  or  lead, 
flattens  out  evenly  to  a  certain  thinness,  and  then  breaks  around 
the  edges.  The  author,  however,  has  succeeded  in  obtaining  a 
malleable  alloy  of  copper  and  iron  which  had  a  perfect  coppery 
appearance  and  lustre,  by  fusing  an  intimate  mixture  of  the  two 
oxides  with  black  flux  in  the  full  heat  of  an  air  furnace.  The 
button  obtained  from  this  experiment  had  all  the  appearance  of 
fine  copper,  laminated  under  the  hammer  to  a  very  thin  sheet 
with  perfectly  unbroken  edges,  and  yielded,  on  analysis,  33  per 
cent,  of  iron.  Arsenic,  antimony,  and  bismuth  form  brittle 
alloys  with  copper. 

HALOID   SALTS. 

Chlorides.  SubcJdoride  of  Copper,  Cu,Cl.  98.89. — "When 
corrosive  sublimate  is  heated  with  half  its  weight  of  copper 
filings,  mercury  passes  over,  and  dichloride  of  copper  remains 


380   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

behind.  Boyle,  who  procured  it  in  this  way,  called  it  resin  of 
copper,  from  its  resemblance  to  common  resin.  Proust  called  it 
white  muriate  of  copper,  and  obtained  it  by  the  action  of  proto- 
chloride  of  tin  on  protochloride  of  copper.  Ignition  of  the  chlo- 
ride with  sugar  in  a  closed  crucible  also  produces  the  subchloride. 
It  is  slowly  deposited  in  crystalline  grains  when  protochloride 
of  copper  is  kept  in  contact  with  metallic  copper.  It  is  deposited 
on  a  plate  of  copper  suspended  in  a  solution  of  the  chloride,  in 
the  form  of  white  tetrahedral  crystals. 

The  dichloride  is  fusible  at  a  heat  just  below  redness,  and 
bears  a  red  heat  in  close  vessels  without  subliming.  Its  color 
varies  with  the  mode  of  preparation,  being  white,  yellow,  or  dark 
brown.  It  is  apt  to  absorb  oxygen  from  the  atmosphere,  forming 
a  green  compound  of  oxide  and  chloride  of  copper.  It  is  insolu- 
ble in  water  or  dilute  sulphuric  acid,  but  dissolves  in  hydro- 
chloric acid,  and  is  precipitated  as  a  white  powder  by  water.  It 
is  also  soluble  in  water  of  ammonia  and  in  a  solution  of  common 
salt. 

Chloride  of  Copper,  CuCl.  62.18. — Sometimes  this  salt  is  pre- 
pared by  double  decomposition,  by  mixing  sulphate  of  copper 
and  chloride  of  sodium  together,  and  crystallizing  the  sulphate 
of  soda  and  excess  of  salt  out  of  the  solution.  It  is  much  better 
obtained  by  dissolving  oxide  or  carbonate  of  copper  in  hydrochlo- 
ric acid,  or  the  metal  in  nitro-hydrochloric  acid. 

Duly  evaporated,  the  solution  thus  obtained  yields  four-sided 
prisms  (CuCl  +  2H0),  of  a  rich  emerald  green  color,  deliquescent 
and  soluble  in  alcohol.  At  212°  they  lose  water,  and  when 
treated  with  cold  sulphuric  acid  all  their  water  is  separated,  and 
brown  anhydrous  chloride  is  left.  This  is  fusible,  and  may  be 
sublimed  unchanged. 

Basic  Chloride  of  Copper,  Cu,Cl,3CuO  +  4HO,  Brunswick 
Crreen. — This  is  a  well-known  pigment,  formed  by  digesting  hy- 
drated  oxide  of  copper  in  a  solution  of  the  chloride,  or  more 
commonly  by  exposing  copper  plates,  moistened  with  sal-ammo- 
niac, to  the  action  of  the  atmosphere.  It  is  a  green  powder,  soluble 
in  acids,  not  in  water.  On  the  application  of  heat,  it  loses  water 
and  becomes  brownish-black. 

When  chloride  of  copper  is  precipitated  by  a  small  quantity 


J 


COPPER.  381 

of  potassa,  a  pale  green  powder  is  thrown  down,  having  the 
composition  CuCl,2CuO-|-4HO.  Heated  strongly,  it  becomes 
black,  all  the  water  being  driven  off,  the.  formula  then  being 
CuCl,2CuO.  Kept  at  208°,  a  brown  compound  is  left,  CuCl,- 
2CuOH-HO.  The  black  substance,  moistened,  becomes  CuCl,- 
2CuO  +  3HO. 

Chloride  of  Copper  and  Ammonium,  CuCl,NH4Cl+2HO. — 
This  salt  is  obtained  by  mixing  saturated  solutions  of  chloride 
of  ammonium  and  chloride  of  copper.  It  crystallizes  in  beauti- 
ful blue  rhombs,  soluble  in  water.  When  warm  chloride  of 
copper  is  saturated  with  ammoniacal  gas,  ammonio-chloride  of 
copper,  CuCl,NH3,  is  formed,  which  is  decomposable  by  water. 
This  dissolves  a  biammonio-chloride,  Cu,Cl,2NH3.  This  is  blue 
and  crystallizable.  A  triammonio-chloride,  CuCl,3NH3,  also 
exists. 

A  double  chloride  of  copper  and  potassium  is  formed  by  cool- 
ing a  strong  mixed  solution  of  the  chlorides  of  the  two  metals. 
It  crystallizes  in  octahedra,  belonging  to  the  quadratic  system, 
of  the  form  KCl,CuCl+2H0.  The  subchloride  used  instead 
of  the  chloride  furnishes  a  double  salt,  2KCl,Cu2Cl,  crystallizing 
in  anhydrous  octahedra  of  the  regular  system. 

Bromide  of  Copper,  CuBr.  115.1. — Oxide  of  copper  dissolved 
in  hydrobromic  acid  and  evaporated,  forms  green  crystals  of 
the  form  CuBr +  5II0,  which,  by  heat,  separate  into  bromide 
and  subbromide,  Cu2Br.  Dry  bromide  absorbs  ammonia,  be- 
coming CuBrjSNHg.  There  are  several  other  ammonio-bromides, 
and  a  basic  salt,  none  of  them  of  any  particular  interest. 

Biniodide  of  Copper,  QnJ..  172.71. — When  a  solution  of 
iodide  of  potassium  is  added  to  another  of  blue  vitriol,  one-half 
the  iodine  escapes,  sulphate  of  copper  remains  in  solution,  and 
a  brownish-white  subiodide  of  copper  with  finely  divided  iodine 
falls.  The  latter  is  washed  off  with  alcohol.  The  subiodide  is 
fusible  and  easily  decomposed  by  nitric  and  sulphuric  acids  and 
by  alkali.  The  iodide  has  not  been  separated.  A  blue  ammo- 
nio-iodide,  however,  exists,  having  the  form  CuI,2NH3+HO. 

Subfiuoride  of  Copper,  Cu^F.  82.18. — Hydrofluoric  acid  brought 
in  contact  with  hydrated  suboxide  of  copper  converts  it  into  a 


382   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

fusible  subfluoride.  The  silico-subfluoride,  3Cu2F,2SiF3,  re- 
sembles it  in  color  and  character. 

Fluoride  of  Copper,  CuFg.  92.93. — Fluoric  acid  forms  with 
black  oxide  of  copper  a  blue  solution,  from  which  the  terfluo- 
ride  separates  in  crystals  containing  2  equivalents  of  water. 
It  forms  green,  soluble,  double  salts,  with  the  alkalies  and 
alumina.  A  basic  fluoride  (CuF,  CuO  +  HO)  is  formed  by  treating 
the  blue  fluoride  with  hot  water. 

A  horofluoride  is  obtained  by  decomposing  sulphate  of  copper 
with  horofluoride  of  barium.  It  separates  in  blue,  deliquescent, 
crystalline  needles,  of  the  form  CuFjBFg.  The  silico-fiuoride  is 
in  blue  prisms,  containing  21  parts  of  water,  2  of  which  are 
separated  by  the  efi'ervescence  of  the  salt. 


OXYSALTS. 

SALTS   OF   THE   SUBOXIDE. 

Sulpliite  of  Suboxide  of  Copper. — When  sulphurous  acid  is 
poured  upon  hydrated  oxide  or  carbonate  of  copper,  a  double 
decomposition  ensues;  thus  3CuO  +  2S02=CuO,S034-Cu20,- 
SO2.  Sulphate  of  copper  is  formed  at  the  expense  of  one  part 
of  the  oxide  and  is  dissolved,  and  the  remaining  dioxide  unites 
with  the  sulphurous  acid,  forming  a  sulphite  of  the  suboxide.  It 
may  be  obtained  in  crystals  by  warming  a  filtered  mixture  of 
the  solutions  of  sulphate  of  copper  and  caustic  potassa,  neutral- 
ized with  sulphurous  acid. 

It  is  a  brilliant  red  salt,  unchangeable  when  dry,  soluble  in 
hydrochloric  and  sulphuric  acids  and  in  ammonia ;  insoluble  in 
water.     Sulphuric  acid  and  heat  decompose  it. 

Hyposulphite  of  Suboxide  of  Copper j  obtained  by  treating  the 
sulphate  with  hyposulphite  of  lime,  is  a  colorless  solution.  It 
forms  several  double  salts  with  potassa  and  soda. 

Silicate  of  Suboxide  of  Copper. — This  is  the  substance  already 
described  as  the  coloring  matter  of  red  glass.  It  is  found  native 
in  the  quartz  which  surrounds  native  copper. 


OXYSALTS.  383 


SALTS  OF  BLACK  OXIDE. 


Sulphate  of  Oopper,  CuOjSOg.  76.81. — This  salt  is  a  common 
product  of  mines  of  sulphuret  of  copper.  The  ore  is  oxidized 
by  the  joint  action  of  air  and  moisture,  and  the  water  which 
trickles  over  it  washes  off  the  newly-formed  sulphate.  This 
natural  process  has  been  imitated  by  manufacturers  who  calcine 
the  native  or  artificial  sulphuret,  lixiviate  it  and  crystallize. 
Addition  of  sulphuric  acid  increases  the  product.  It  is  also 
obtained  by  dissolving  the  metal  in  moderately  dilute  sulphuric 
acid  and  crystallizing. 

As  prepared  by  the  first  two  processes,  it  is  always  impure, 
containing  sulphate  of  iron.  This  may  be  in  great  measure 
separated  from  it  by  calcination,  which  decomposes  the  sulphate 
of  iron,  leaving  the  oxide,  but  does  not  affect  the  blue  vitriol. 
The  copper  may  also  be  precipitated  by  means  of  iron  and  redis- 
solved  in  sulphuric  acid. 

Pure  sulphate  of  copper  is  a  clear  azure  blue  salt,  crystallizing 
in  elongated  rhombs  of  the  doubly  oblique  rhombic  or  triclinate 
system.  These  contain  32  parts  of  oxide  of  copper,  32  of  sul- 
phuric acid,  and  36  of  water  in  the  hundred  parts,  and  may  be 
expressed  by  the  formula  CuOjSOj+SHO.  A  small  quantity 
of  iron  is  recognized  by  the  greenish  cast  it  gives  to  the  crystals, 
and  especially  to  their  effloresced  surfaces.  The  specific  gravity 
of  the  salt  is  2.274.  Exposed  to  the  atmosphere,  it  parts  with 
a  quantity  of  its  water  and  effloresces ;  at  212°  it  loses  4 
equivalents  of  water;  at  430°,  it  parts  with  the  remaining 
atom,  leaving  the  anhydrous  sulphate  as  a  white,  opaque,  pul- 
verulent mass.  The  anhydrous  salt  is  obtained  in  colorless 
crystals  by  the  action  of  cold  sulphuric  acid  on  copper  in  close 
vessels.  However  obtained,  it  attracts  water  from  the  atmo- 
sphere. Strong  ignition  expels  its  acid,  and,  if  carbon  be  pre- 
sent, sulphuret  of  copper  and  metallic  copper  remain  at  a  high 
temperature,  and  metal  alone  at  a  low  one. 

Basic  Sulphate  of  Copper. — A  compound  of  this  sort  forms 
the  basis  of  the  mineral  Brochantite.  It  is  prepared  artificially 
by  precipitating  the  sulphate  already  described  with  a  small 


384     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

quantity  of  alkali,  by  digesting  fresh  carbonate  or  hydrate  of 
copper  in  a  solution  of  blue  vitriol,  or  by  exposing  ammonio- 
sulphate  to  the  action  of  the  air.  It  is  pale  green,  insoluble, 
easily  decomposed  by  heat  into  water,  oxide  and  sulphate  of 
copper.  It  is  supposed  to  be  a  mixture  of  two  basic  salts,  and 
the  expression  for  it  will  be  found  between  the  formulae  4CuO, 
SO3+4HO  and  3CuO,S03+3HO.  Kane  says  that,  by  exactly 
precipitating  blue  vitriol  with  caustic  potassa,  he  obtained 
another  basic  salt,  the  composition  of  which  is  8CuO,S03+12HO. 

Sulphate  of  Coijper  and  Ammonia. — There  are  several  double 
salts  of  copper  formed  with  ammonia  and  potassa.  The  ammo- 
niacal  double  salts  vary  much  in  color  and  composition.  When 
solutions  of  the  two  sulphates  of  copper  and  ammonia  are  mixed, 
and  duly  concentrated,  we  obtain  light  blue,  very  soluble  crys- 
tals, of  the  form  NH,0,S03+CuO,S03+6HO.  When  carbonate 
of  ammonia  and  sulphate  of  copper  are  rubbed  together  in  a 
mortar,  the  mass  becomes  blue,  effloresces  and  grows  moist,  and 
another  double  salt  is  formed.  When  a  strong  solution  of  blue 
vitriol  is  treated  with  water  of  ammonia  till  the  insoluble  sub- 
salt  first  thrown  down  is  all  dissolved,  we  obtain  an  ultramarine 
blue  solution,  from  which,  by  gradual  evaporation,  cold,  or  the 
addition  of  alcohol,  blue  prisms  of  ammonio-sulphate  of  copper 
separate.  Their  formula  is  2NH3+CuO,S03  4-HO.  They  are 
soluble  in  2^  parts  of  water,  and  decompose  in  the  air.  At 
300°  they  become  apple  green,  having  parted  with  their  water 
and  one  equivalent  of  ammonia,  and  at  400°  one-half  of  this  is  dis- 
pelled. Dry  sulphate  of  copper  absorbs  53.97  per  cent,  of  ammo- 
niacal  gas,  forming  a  soluble  blue  powder,  5NH3+2(CuO,S03). 

Sulphate  of  Cojjper  and  Potassa  is  a  light  blue  salt,  formed 
by  crystallizing  the  mixed  solution  of  the  sulphates.  It  is 
KO,S03-l-CuO,S03+6HO.  It  loses  two  equivalents  of  water 
at  212°,  and  deposits  a  green  basic  double  salt  on  boiling.  The 
double  sulphate  with  soda  is  formed  in  the  same  manner  from 
blue  vitriol  and  bisulphate  of  soda.  A  salt  composed  of  the 
sulphates  of  copper,  soda,  and  magnesia,  may  be  formed  by 
mixture  and  crystallization. 

Hyposulphate  of  Copper,  CuO,S205-l-4HO. — When  sulphate 
of  copper  is  exactly  decomposed  by  hyposulphate  of  baryta, 


OXYSALTS.  385 

and  the  solution  concentrated,  rhombic  prisms  soluble  in  water 
are  obtained,  from  which  a  small  quantity  of  ammonia  precipi- 
tates a  basic  hyposulphate,  and  with  which  an  excess  of  the 
same  reagent  forms  a  double  salt  which  crystallizes  in  azure 
square  tables,  difficult  of  solution,  permanent  in  the  air,  and 
composed  of  2NH3+ CuOjS^O,. 

Phosphate  of  Copper,  2CuO,P05.  111.11.— Phosphate  of 
soda  throws  down  from  a  soluble  salt  of  copper,  the  above  salt 
as  a  greenish  powder,  insoluble  in  water,  soluble  in  acids,  becom- 
ing brown  by  heat.  A  number  of  basic  phosphates  have  been 
found  native.  The  phosphite  and  the  hypophospMte  of  copper 
possess  no  particular  interest. 

Nitrate  of  Copper. — When  nitric  acid  is  poured  upon  metallic 
copper,  violent  action  takes  place  even  in  the  cold.  Strong 
effervescence  ensues;  heat  is  evolved ;  copious,  dense,  red  fumes 
rise,  and  a  blue  solution  is  obtained.  The  reaction  will  be 
understood  by  a  glance  at  the  formula.  Thus  3Cu-f4N05  = 
3(CuO,N05)  +  N02.  The  deutoxide  of  nitrogen  as  it  rises 
absorbs  oxygen,  and  forms  the  red  fumes  of  nitrous  acid.  To 
obtain  the  solution,  concentrated  nitric  acid  must  not  be  used, 
as  a  green  basic  insoluble  salt  will  subside.  The  crystals, 
obtained  from  this  solution  at  low  temperatures,  contain  6 
equivalents  of  water  ;  those  procured  at  high  temperatures  only 
3(CuO,N05+3HO).  The  crystals,  which  are  fine  blue  prisms, 
are  highly  deliquescent,  and  it  is  almost  impossible  to  keep 
them.  They  deflagrate  on  redhot  coals,  and  behave  generally 
like  other  nitrates.  Powdered  and  rolled  in  tin-foil,  they  are 
spontaneously  ignited.  The  basic  salt,  3CuO,NOj+HO,  is 
formed  by  heating  the  neutral  salt  in  solution  with  a  little  alkali. 
It  is  a  green  powder,  soluble  in  acids,  not  in  water,  easily  reduced 
by  a  red  heat  to  a  black  oxide,  as  is  the  crystallized  nitrate. 
Treated  with  ammonia,  it  forms  the  ammonio-nitrate,  the  for- 
mula of  which  is  2NH3+CuO,N03. 

Carbonate  of  Copper. — This  compound  occurs  native  in  the 

beautiful  green  and  blue  malachites.     It  is  obtained  artificially 

by  precipitating  it  from  a  hot  solution  of  copper  with  an  alkaline 

carbonate.     When  precipitated  from  a  cold  solution,  it  is  mixed 

25 


386      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

with  the  hydrate,  and  contains  a  large  quantity  of  water.    lire's 
formulae  for  this  salt  are  : — 

2(CuO,C02)  +  CuO,HO. 
CuO,C02+2(CuOHO). 

Borate  of  Co'pper  is  a  pale  green  powder,  slightly  soluble  in 
water,  fusing  to  a  green  glass.  It  may  be  obtained  by  fusing 
borate  of  soda  and  oxide  of  copper  together  and  dissolving  out 
the  soda,  or  by  double  decomposition. 

Silicate  of  Cojjper  occurs  native  as  a  fine  apple  green  com- 
pound, usually  in  botryoidal  shapes.  It  is  formed  by  fusing 
oxide  of  copper  with  glass,  and  has  a  green  tint. 

Acetates  of  Qopper. — There  is  quite  a  number  of  these  salts. 
The  neutral  acetate,  obtained  by  dissolving  verdigris  in  acetic 
acid,  or  by  precipitating  an  equivalent  of  sulphate  of  copper 
with  an  equivalent  of  neutral  acetate  of  lead,  crystallizes  in  dark 
green,  oblique  rhombic  prisms,  with  oblique  terminating  planes. 
Verdigris  has  been  called  a  bibasic  acetate  of  copper,  but  analy- 
ses of  it  do  not  very  closely  correspond  with  its  theoretical 
composition.  It  is  a  green  salt,  largely  used  in  the  arts.  It  is 
formed  by  the  action  of  vinegar  upon  plates  or  sheets  of  copper. 

Arsenites  of  Copper.  Scheele's  G-reen. — This  fine  pigment  is 
formed  by  precipitating  sulphate  of  copper  with  arsenite  of  po- 
tassa.  The  Schweinfurth  green,  which  is  a  richer  pigment,  is 
made  by  boiling  strong  solutions  of  acetate  of  copper  and  arse- 
nious  acid  together.  It  is  a  mixture  of  arsenite  and  acetate  of 
copper.  There  is  another  arsenite  of  copper  (2CuO,As03), 
which  is  precipitated  neither  by  acids  nor  alkalies,  and  which 
furnishes  a  yellowish-green  salt  by  evaporation.  It  is  made  by 
digesting  the  oxide  or  the  carbonate  of  copper  in  arsenious  acid. 


ZINC.  387 


CHAPTER    y. 

ZINC. 

This  metal  was  first  mentioned  by  Paracelsus,  under  the 
name  of  zinctum,  in  the  16th  century.  Its  most  abundant  ore  is 
the  sulphate  or  blende,  but  calamine,  a  mixture  of  silicate  and 
carbonate,  is  more  easily  worked.  It  is  known  in  commerce  by 
the  name  of  spelter. 

METALLURGIC   TREATMENT    OF    ZINC    ORES. 

When  sulphuret  of  zinc  is  to  be  smelted,  it  is  always  roasted 
so  as  to  drive  off  the  sulphur  and  convert  it  into  an  oxide.  This 
is  commonly  done  in  a  reverberatory  furnace.  It  is  then  va- 
riously treated  in  the  different  countries  in  which  it  is  smelted. 

In  Silesia,  the  roasted  ore  is  mixed  with  its  own  volume  of 
coal-cinder  and  introduced  into  redhot  muffles.  These  muffles 
are  furnished  with  a  conical  neck  and  two  openings,  through 
one  of  which  the  zinc  is  drawn  off,  and  through  the  other  a 
fresh  charge  of  ore  is  introduced.  A  single  square  furnace  con- 
tains 10  muffles,  5  on  a  side,  heated  by  a  single  fire.  Every 
ton  of  metal  requires  from  11  to  12  tons  of  coal  for  its  reduc- 
tion, and  33  muffles  are  destroyed  for  every  50  tons  of  metal. 
The  annual  production  of  Silesia  is  from  7000  to  8000  tons  of 
zinc. 

At  Liege,  earthen  tubes,  about  3  feet  long  and  4  or  5  inches  wide, 
holding  about  40  pounds,  are  used  for  the  reduction.  They  rest 
on  fire-brick  only  at  either  end,  the  rest  of  the  tube  being  exposed 
to  the  fire.  They  terminate  at  one  end  in  cast-iron  tubes,  which 
contract  in  diameter  from  one  to  one  and  a  half  inch.  Each  fur- 
nace contains  22  such  tubes  laid  horizontally  in  rows.  The  heat 
from  a  single  fire  plays  freely  over  them.  Into  the  earthen  tubes 
the  roasted  ore,  mixed  with  from  one-half  to  two-thirds  of  its  weight 


388     CHEMISTRY  OP  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  fine  coke,  is  introduced.  Heat  is  applied,  and  the  condensed 
metal  is  drawn  oiF,  every  two  hours,  from  the  cast-iron  tubes. 

The  English  use  covered  crucibles,  with  openings  in  the  bot- 
tom, communicating  with  short  conical  tubes  of  sheet-iron,  to 
each  of  which,  during  the  process  of  smelting,  a  long  sheet-iron 
tube  is  attached.  These  are  heated  in  a  circular  cupola  fur- 
nace, resembling  a  glass  furnace,  set  in  a  high  conical  chimney 
with  a  strong  draught.  The  cupola  has  several  openings  in  it, 
through  which  the  smoke  and  flame  pass.  The  fire  is  made  in  the 
centre,  and  heats  all  the  pots.  The  mixed  ore  and  coal  are  placed 
in  these  pots,  the  hole  in  the  bottom  of  which  is  closed  with  a 
plug,  and  heated.  At  first  a  brown  flame,  containing  cadmium 
and  arsenic,  arises,  then  a  bluish-white  blaze  plays  over  the  sur- 
face. This  is  the  signal  for  putting  the  covers  on  the  crucibles, 
as  it  shows  that  the  volatilization  of  the  zinc  has  begun.  The 
plug  is  now  charred,  and  the  vapors  of  zinc  descend  through  the 
sheet-iron  tubes  and  are  condensed  in  a  vessel  of  water,  in  which 
they  terminate.  When  the  tubes  become  choked,  they  are  cleaned 
out  with  a  redhot  iron  rod.  The  consumption  of  coal  is  about 
12  tons  to  every  1  of  metal.  The  granulated  zinc  is  submitted 
to  a  second  distillation. 

The  theory  of  these  processes  is  simple.  The  roasting  drives 
ofi"  sulphur,  and  the  resulting  oxide,  mixed  with  coal  and  heated, 
is  reduced,  carbonic  acid  being  given  oif.  The  volatile  metal, 
passing  off,  is  first  liquefied  and  then  solidified. 

ZINC   AND   NON-SALINE   COMPOUNDS. 

Zinc. — The  commercial  metal  is  never  pure.  The  best  va- 
rieties are  the  Vieille  Montague  and  New  Jersey  zinc.  The 
most  of  the  zinc  in  the  market  is  extremely  impure,  containing 
iron,  lead,  cadmium,  arsenic,  carbon,  &c.  It  is  impossible  to 
get  rid  of  these  in  the  dry  way  by  any  process  yet  invented. 

The  only  method  is  to  dissolve  the  metal.  If  sulphuric  acid 
be  selected  as  the  solvent,  it  will  at  once  rid  us  of  the  lead, 
especially  if  some  alcohol  be  added  to  the  moderately  dilute  solu- 
tion, as  this  metal  then  falls  to  the  bottom  as  an  insoluble  sul- 
phate.    If  a  stream  of  sulphuretted  hydrogen  be  passed  through 


( 


ZINC.  389 

the  acid  solution,  tlie  cadmium  and  arsenic  are  precipitated. 
The  iron  is  now  thrown  down  bj  carbonate  of  ammonia,  which 
is  added  in  sufficient  quantity  to  redissolve  whatever  zinc  may 
have  fallen.  The  filtered  solution  is  now  evaporated  to  dryness, 
ignited,  mixed  with  finely  levigated  charcoal,  and  distilled.  A 
second  distillation  removes  what  carbon  it  may  retain  from  the 
reduction. 

It  is  a  bluish-white,  brilliant,  crystalline  metal,  "with  large 
laminae.  It  may  be  obtained  in  six-sided  prisms.  It  is  so  hard 
that  the  file  does  not  readily  act  on  it.  At  ordinary  temperatures 
it  is  somewhat  brittle,  and  at  400°  so  much  so  as  to  be  pulver- 
izable  in  a  mortar.  At  200°  or  300°,  however,  it  may  be  rolled 
into  sheets  or  drawn  into  wire.  It  remains  unaltered  in  dry  air, 
but  in  moist  air  it  becomes  dull.  It  does  not  decompose  pure 
water,  but  when  ignited  it  resolves  steam  into  its  elements. 
Acidulated  water  is  rapidly  decomposed  by  it,  alkaline  slowly. 

The  specific  gravity  of  pure  fused  zinc  is  6.9  ;  of  the  common 
rolled  metal,  7.19.  It  fuses  at  773°;  volatilizes  at  a  white 
heat,  and  burns  in  the  air. 

This  metal  shrinks  but  little  as  it  cools,  so  that  it  retains  upon 
its  surface  any  interstices  or  irregularities  of  the  mould  in  which 
it  is  cast.  On  this  account,  as  well  as  by  reason  of  its  cheapness, 
it  has  been  used  by  dentists  to  take  copies  of  their  plaster-moulds 
of  the  mouth,  for  the  purposes  of  plate-work.  Bronze  is  an  alloy 
w^iich  possesses  the  property  of  expanding  during  cooling  in  a 
very  high  degree,  accurately  representing,  when  well  fused,  the 
most  minute  peculiarities  of  the  matrix,  and  would,  consequently, 
do  better  work.  Its  price,  and  the  difficulties  to  be  encountered 
in  its  management,  will  probably  prove  an  obstacle  to  its  general 
adoption.  The  beautiful  statuettes  of  Berlin  iron,  as  the  material 
is  called,  so  much  admired  for  their  sharpness  of  outline,  are  often 
made  of  zinc,  but  the  fine  efi'ect  of  their  surface  is  manifestly  ob- 
tained by  careful  chasing.  Zinc  may  be  made  much  more  sensi- 
tive to  the  inequalities  of  the  mould  by  mixing  it  with  tin,  and  a 
combination  of  this  kind  is  used  instead  of  pure  zinc  by  many 
dentists.  Zinc,  alloyed  with  copper,  on  the  other  hand,  or  lead, 
has  a  tendency  to  contract,  and  consequently  to  withdraw  its 
surface  from  the  inequalities  of  the  mould. 


390      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Its  symbol  is  Zn.  Its  equivalent  is  32.527  on  the  hydrogen, 
and  406.59  on  the  oxygen  scale. 

Oxide  of  Zinc,  ZnO.  40.54. — When  metallic  zinc  is  heated  in 
an  open  crucible,  it  burns  with  great  rapidity,  sending  up  a 
bright  bluish-white  blaze,  which  lets  fall  a  very  light,  downy, 
flocculent  substance,  formerly  called  lana  2^Jt'ilosophica,  or  phi- 
losopher's wool,  and  more  recently  flowers  of  zinc.  It  is  the 
oxide.  The  same  substance  may  be  obtained  by  igniting  the 
precipitated  carbonate  of  zinc,  and,  in  the  form  of  a  hydrate, 
by  precipitating  a  solution  of  zinc  by  less  potassa  than  is  neces- 
sary to  throw  it  all  down. 

When  hot,  it  is  straw  or  lemon  yellow,  but,  if  it  be  pure,  it 
becomes  white  again  on  cooling.  It  is  insoluble  in  water,  but, 
being  a  strong  salifiable  base,  it  unites  readily  with  acids.  It 
also  forms  compounds  with  some  of  the  alkalies. 

The  salts  of  this  oxide  are  colorless,  generally  soluble  in 
water,  communicating  to  it  a  disagreeable  styptic  taste.  The 
caustic  alkalies  throw  down  a  white  precipitate,  soluble  in  ex- 
cess. The  carbonates  produce  a  white  precipitate,  carbonate  of 
ammonia  being  the  only  one  which  redissolves  it  when  added  in 
excess.  The  oxide  being  soluble  in  salts  of  ammonia  generally, 
these  prevent  its  precipitation.  Sulphuretted  hydrogen  throws 
down  all  the  zinc  as  a  sulphuret  from  its  solution  in  a  feeble 
acid  or  from  an  alkaline  solution.  Alkaline  sulphurets  precipi- 
tate from  any  solution. 

The  gray  film  formed  on  zinc  exposed  to  the  air  has  been 
called  a  suboxide,  but  appears  to  be  a  mixture  of  the  oxide  and 
metallic  zinc.  Thenard  speaks  of  a  peroxide  obtained  by  the 
action  of  peroxide  of  hydrogen  on  the  hydrated  oxide.  The 
native  crystallized  oxide  is  red. 

Sulphuret  of  Zinc,  ZnS.  48.66. — This  compound  is  found 
native  in  blende.  When  obtained  by  igniting  the  dry  oxide  or 
sulphate  with  sulphur,  or  the  latter  with  charcoal,  it  is  yellowish 
or  white.  The  hydrate  procured  by  precipitating  the  solution 
of  the  oxide  by  an  alkaline  sulphuret  is  white.  Both  are  fusible 
at  a  high  heat,  and  oxidized  by  roasting  or  by  the  strong  acids. 
Hydrogen  passed  over  ignited  sulphate  of  zinc,  leaves  a  yellow 
powder,  ZnO, ZnS. 


ZINC.  391 

PJwsphuret  of  zi7ic  is  a  lead-colored  metallic  mass,  formed  by 
throwing  phosphorus  in  melted  zinc.  It  is  slightly  malleable. 
Carburet  exists  in  commercial  metallic  zinc. 

ALLOYS. 

The  most  important  alloys  of  zinc  have  already  been  men- 
tioned under  the  head  of  Copper.  It  alloys  readily  with  potas- 
sium and  sodium,  not  easily  with  arsenic  and  antimony,  and  not 
at  all  with  bismuth.  In  small  quantity  it  unites  with  iron, 
which,  when  coated  with  it,  goes  by  the  name  of  galvanized  iron. 
It  protects  iron,  but  is  itself  more  subject  to  corrosion.  It  has 
been  shown  that  when  it  contains  the  latter  metal,  it  dissolves 
in  acids  far  more  readily  than  when  pure,  and  that,  under  caustic 
potassa  in  contact  with  iron,  it  dissolves  twelve  times  more 
rapidly  than  when  in  the  same  relation  to  platinum.  Alloyed 
with  tin,  it  forms  spurious  silver  leaf. 

HALOID    SALTS. 

Chloride  of  Zinc,  ZnCl.  67.96. — This  compound  is  formed, 
with  evolution  of  heat  and  light,  when  zinc  filings  are  intro- 
duced into  chlorine  gas.  It  is  also  obtained  by  dissolving 
the  metal  in  hydrochloric  acid,  and  distilling  over  the  volatile 
chloride,  the  remainder  being  oxychloride,  or  heating  it  in  a 
tube  through  which  dry  hydrochloric  acid  gas  is  passed.  One 
part  of  zinc  filings  distilled  with  two  of  chloride  of  mercury,  or 
one  part  sulphate  of  zinc  with  two  of  common  salt,  produce  the 
same  substance. 

Thus  obtained,  it  is  a  soft  white  solid  at  ordinary  tempera- 
tures, and  hence  called  butter  of  zinc.  It  fuses  at  a  heat  a  little 
above  212°,  sublimes  at  a  red  heat,  and  deliquesces  in  the  air. 
It  is  soluble  in  alcohol,  and  crystallizes  out  of  the  solution  in 
combination  with  the  solvent.  From  a  highly  concentrated 
aqueous  solution  it  may  be  obtained  in  crystals  of  ZnCl -f  HO. 

There  are  several  basic  chlorides.  When  zinc  is  boiled  with 
its  chloride  as  long  as  hydrogen  comes  over,  or  when  the  chlo- 
ride is  incompletely  precipitated  by  ammonia,  a  white  powder 
results,  which  is  ZnCl-f3ZnO  +  4HO. 


392      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

This  cliloride  forms  double  salts  with  the  alkaline  chlorides. 
The  double  salt  with  ammonium  is  used  for  tinning  iron  or 
copper.  When  rubbed  on  the  heated  surface  of  the  metal,  the 
oxides  present  form  double  chlorides  with  the  zinc  salt,  and 
ammonia  is  set  at  liberty,  leaving  a  clean  surface  for  the  coating 
metal. 

Iodide  of  Zinc,  ZnS. — Iodine  and  water,  digested  on  zinc 
filings,  give  rise  to  a  colorless  solution,  which  is  evaporated  to  a 
deliquescent  iodide.  By  heat,  in  close  vessels,  it  sublimes  in 
brilliant  acicular  crystals.  Heated  in  the  air,  it  decomposes  into 
protoxide  of  zinc  and  iodine. 

There  are  several  basic  and  double  iodides.  Iodide  of  potas- 
sium and  nitrate  of  zinc  mixed  together  form  a  peculiar,  soluble, 
crystallizable  double  salt,  insoluble  in  alcohol,  consisting  of 
iodide  of  zinc  and  nitrate  of  potassa. 

Bromide  of  Zinc,  ZnBr. — This  salt  is  obtained  by  dissolving 
the  oxide  in  hydrobromic  acid.  It  dissolves  in  water,  alcohol, 
and  ether,  crystallizes  with  difficulty,  fuses  at  a  red  heat,  and 
in  close  vessels  sublimes  in  needles.  Heated  in  the  air,  it  forms 
oxybromide.  Ammonia  unites  with  it  to  form  a  crystallizable 
salt. 

Fluoride  of  Zinc,  ZnF. — This  salt  is  made  like  the  bromide. 
It  crystallizes,  dissolves  with  difficulty  in  pure  water,  easily  in 
water  acidulated  with  hydrofluoric  acid.  There  are  several 
double  salts,  with  potassium,  aluminum,  &c.,  and  with  the  me- 
talloids. 

OXYSALTS. 

Sulphate  of  Zinc,  ZnO,S03. — This  salt  may  be  made  by  cal- 
cining the  sulphuret,  or  by  dissolving  the  metal  or  its  carbonate 
in  sulphuric  acid.  The  same  precautions  must  be  observed,  in 
order  to  insure  purity,  as  have  been  already  described  under 
the  head  of  metallic  zinc. 

It  is  isomorphous  with  Epsom  salts,  and,  like  it,  crystallizes  in 
different  forms  and  with  different  proportions  of  water.  Crys- 
tallized from  a  cold  solution,  it  contains  7  equivalents  of  water, 
from  a  hot  one,  6.     By  treating  the  former  with  alcohol,  or 


ZINC.  393 

adding  excess  of  acid  to  the  crystallizing  solution,  the  salt  retains 
only  2  equivalents  of  water.  AVhen  boiled  with  alcohol  of  860°, 
the  salt  has  5H0.  At  32°,  100  parts  of  water  dissolve  43.02 
of  the  anhydrous  salt,  and  at  212°,  95.03.  It  is  insoluble  in 
alcohol  stronger  than  .88.  The  dry  salt  is  decomposed  only 
at  a  very  high  and  long  continued  heat.  It  forms  a  great 
variety  of  basic  and  ammoniacal  salts. 

Sulphite  of  Zinc. — This  salt  crystallizes  from  a  solution  of 
the  oxide  in  sulphurous  acid.  It  is  soluble  in  sulphurous  acid, 
precipitated  by  alcohol.     Its  formula  is  ZnO,S024-2HO. 

Dithionate  of  Zinc,  ZnO,S205  4-6HO,  is  formed  by  mixing 
sulphate  of  zinc  and  dithionate  of  baryta.  It  is  very  soluble, 
diflScult  of  crystallization,  and  forms  a  double  salt  with  ammonia. 

Ditliionite  of  Zinc  is  formed  when  the  metal  is  digested  in 
liquid  sulphurous  acid.  Sulphite  and  hyposulphite  are  formed, 
for  ZnO  +  3S02=ZnO,S2024-ZnO,S02.  The  sulphite  may  be 
precipitated  by  alcohol,  or  converted  into  dithionite  by  digestion 
in  a  closed  vessel  with  sulphur.  Evaporated  to  a  syrupy  con- 
sistence, and  exposed  for  a  long  time  to  the  air,  sulphuret  of 
zinc  is  precipitated,  and  the  solution  contains  trithionate  of 
zinc. 

Nitrate  of  Zinc,  ZnOjNO.^ — Zinc  dissolves  in  nitric  acid,  and 
the  solution,  concentrated  to  the  consistence  of  a  syrup,  lets  fall 
deliquescent  prisms,  soluble  in  alcohol,  having  the  form  ZnO,- 
NO3+6IIO.  Three  parts  of  water  are  expelled  by  heat,  and 
when  farther  heat  is  applied,  water  and  acid  pass  off,  leaving 
basic  salts. 

Pliosphate  of  Zinc,  2ZnO,P0.5 — Phosphate  of  soda  added  to 
sulphate  of  zinc,  throws  down  this  salt  as  a  white  insoluble 
powder,  which,  dissolved  in  phosphoric  acid,  becomes  an  acid 
salt.  The  basic  salt,  3ZnO,P05+2HO,  is  gelatinous,  becoming 
granular,  and  is  obtained  by  adding  basic  phosphate  of  soda  or 
ammonia  to  a  solution  of  sulphate  of  zinc.  Both  phosphates 
fuse  to  a  clear  glass.     It  forms  double  salts  with  ammonia. 

The  jjhosphite  is  white,  and  somewhat  soluble.  The  hi/po- 
pliospliite  is  very  soluble,  and  difficult  to  crystallize. 

Perclilorate  of  Zinc,  ZnO,C107. —  Silico-fluoride  of  zinc  and 
perchlorate  of  potassa,  mixed,  form  this  salt,  which  is  deliques- 


394   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

cent  and  crystallizable.  The  chlorate  is  similarly  obtained  from 
chlorate  of  potassa.  The  hypochlorite  is  formed  by  the  direct 
action  of  hypochlorous  acid  on  hydrated  oxide  or  carbonate  of 
zinc. 

The  Bromate  is  obtained  in  like  manner,  and  the  iodate  by 
mixing  equivalents  of  sulphate  of  zinc  and  iodate  of  soda. 
Both  form  double  salts  with  ammonia. 

Carbonate  of  Zinc,  ZnOjCOj- — This  salt  is  found  native  as 
calamine.  The  precipitate  from  mixed  solutions  of  sulphate  of 
zinc  and  carbonated  alkali,  is  a  mixed  carbonate  and  hydrate 
(ZnO,C02+ZnO  +  3HO),  and(2  (ZnO,C02)  +  3ZnO  +  3HO),  and 
probably  others.  Wcihler  obtained  it  in  crystals  by  exposing  a 
solution  of  oxide  of  zinc  in  carbonate  of  potassa  to  the  air. 
Kane  declares  this  to  be  a  double  carbonate.  Double  salts  are 
formed  with  soda  and  ammonia. 

Borate  of  Zinc  fuses  to  a  yellow  glass.  Its  formula  is  ZnO,- 
2BO3.  Silicate  of  zinc  occurs  native,  mixed  with  carbonate,  as 
electric  calamine. 


CHAPTER   VI. 

TIN. 

This  metal  was  known  to  the  ancients,  who  obtained  it  chiefly, 
if  not  exclusively,  from  Cornwall.  It  is  mentioned  by  Moses, 
and  the  Phoenicians  are  supposed  to  have  obtained  it  from  the 
Cornish  mines,  at  least  five  hundred  years  before  the  Christian 
era. 

It  occurs  native  in  two  forms,  the  oxide  and  the  sulphuret. 
The  oxide  is  found  in  granite  and  porphyry  rocks,  in  veins  and 
beds,  and  in  alluvial  deposits,  in  small  rounded  grains.  The 
latter  variety  of  tin  is  called  stream  tin,  and  is  a  very  pure  oxide. 
The  purest  grain  tin  is  obtained  from  it.  The  sulphuret,  or 
tin  pyrites,  is  not  important  as  a  working  ore,  the  oxide,  or  tin- 
stone, alone  having  been  found  in  sufficient  quantity  for  metal- 


TIN.  395 

lurgic  purposes.  Its  principal  localities  are  Cornwall,  Bohemia, 
Saxony,  Malacca,  and  Banca. 

The  crude  ores  are  crushed  and  washed  to  a  certain  degree  of 
richness,  and  a  rough  assay  is  taken  by  reducing  the  ore  in  a 
crucible  with  coal  broken  finely.  This  imperfect  operation  is 
necessary  to  give  the  smelter  an  idea  of  the  yield  of  the  ore  in 
the  large  way.  The  ores  are  roasted  in  order  to  drive  off  sulphur 
and  arsenic,  which  are  collected  in  chambers  arranged  for  their 
reception.  As  copper  pyrites  is  often  contained  in  tin  ores,  the 
roasted  ore  is  thrown  into  vats,  which  are  stirred  up  with  wooden 
rakes.  The  sulphate  of  copper,  formed  in  the  roasting,  is  thus 
dissolved  out.  It  is  subsequently  precipitated  by  means  of 
metallic  iron,  and  all  the  copper  thus  obtained. 

The  ores  are  reduced  in  two  ways,  by  the  reverberatory  and 
the  blast  furnaces.  When  the  first  of  these  is  used,  the  ore  is 
mixed  with  coal  and  a  little  slacked  lime.  The  heat  is  low  at 
first,  to  prevent  the  formation  of  an  enamel  with  the  oxide  of 
tin,  and  is  very  gradually  raised,  the  doors  being  all  closed. 
The  doors  are  thrown  open  after  6  or  8  hours'  fusion,  the 
bath  stirred  up  to  complete  the  separation  of  the  tin,  and  the 
scoriae  raked.  The  uppermost  of  these,  about  three-fourths  of 
the  whole,  are  poor,  and  are  thrown  away.  Those  next  below 
are  stamped,  and  those  resting  immediately  upon  the  surface  of 
the  metal  are  directly  fused  again  for  grain  tin.  The  metal  is 
run  out  into  pig. 

The  process  of  refining  consists  of  two  distinct  operations, 
liquation  and  refining  proper.  The  metals  combined  with  tin 
are  principally  copper,  iron,  arsenic,  and  tungsten,  with  some 
sulphurets  and  arseniurets  that  have  not  been  oxidated,  some 
unreduced  oxides,  and  unfused  earthy  matters. 

Liquation  is  accomplished  by  laying  the  blocks  of  metal  on 
the  hearth  of  a  reverberatory  furnace,  and  raising  the  tempera- 
ture to  the  melting  point  of  tin.  This  metal  is  sweated  out 
from  the  pores  and  runs  into  the  proper  refining  basin,  leaving 
a  highly  ferruginous  alloy.  Fresh  tin  blocks  are  placed  on  the 
last,  and  the  liquation  continued  till  the  refining  basin  is  full. 

Billets  of  green  Avood  are  now  plunged  into  the  tin-bath,  and 
the  gas  disengaged  from  them  produces  a  violent  ebullition.     A 


396      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

froth,  composed  chiefly  of  the  oxides  of  tin  and  of  the  foreign 
metals,  rises  to  the  surface,  and  is  skimmed  off  and  returned  con- 
tinually to  the  furnace.  When  the  refining  is  supposed  to  be 
accomplished,  the  billets  are  lifted  out,  and  the  metals  suffered 
to  arrange  themselves  in  the  order  of  their  specific  gravity. 
Three  zones  or  layers  of  metal  are  found,  the  lowest  of  which 
is  full  of  impurities,  that  above  is  much  better,  and  the  upper 
one  nearly  pure  tin.  The  settling  being  complete,  the  metal  is 
ladled  out.  That  from  the  bottom  is  so  impure  that  it  must  be 
refined  anew,  as  if  it  had  been  just  taken  from  the  ore.  The 
operation  of  tossing  is  sometimes  substituted  for  this.  It  con- 
sists in  lifting  up  the  melted  metal  in  a  ladle  and  letting  it  fall 
again,  so  as  to  agitate  the  whole  mass.  The  froth  is  skimmed 
off,  and  the  metal  allowed  to  settle  as  before. 

The  residuary  blocks  of  the  liquation  are  now  fused  at  a  higher 
heat,  and  an  impure  metal  is  run  off  and  allowed  to  settle.  The 
upper  portions  are  subjected  to  a  second  refining,  the  lower  are 
too  impure  for  use. 

Reduction  by  the  blast  furnace  is  used  for  the  finest  varieties 
of  commercial  tin.  The  stream  tin  is  usually  selected.  It  is 
carefully  picked  and  well  stamped  and  washed.  It  is  mixed 
with  slugs  and  scoriae  and  smelted  Avith  wood  charcoal.  The 
fused  metal  is  run  first  into  a  receiving  basin,  Avhere  it  is  al- 
lowed to  settle  for  a  time,  when  the  upper  layer  of  metal  is 
transferred  to  the  refining  basin,  and  the  lower  sent  back  to  the 
furnace. 

Refined  tin  is  the  name  given  to  the  upper  layer  of  metal  re- 
sulting from  the  refining  process.  Block  tin  is  the  second  class 
metal.  G-rain  tin  is  made  by  heating  a  block  till  it  gets  brittle, 
and  then  letting  it  fall  from  a  height,  when  it  breaks  up  into 
numerous  grains  or  tears. 

TIN   AND    ITS   NON-SALINE    COMPOUNDS. 

Commercial  tin  almost  always  contains  impurities.  These 
may  be  got  rid  of  by  a  plan  resembling  the  refining  of  tin  al- 
ready described.  The  metal  may  be  kept  fused  for  some  time 
till  the  separation  of  the  strata  and  the  subsidence  of  the  heavier 


TIN.  397 

and  impure  alloys  takes  place,  or  it  may  be  stirred  to  oxidate 
the  combined  metals  with  a  portion  of  the  tin  ;  or,  last  and  best, 
it  may  be  converted  into  oxide  by  the  action  of  nitric  acid, 
washed  with  muriatic  acid  and  water,  and  reduced  with  carbon. 

It  is  a  brilliant  white  metal,  resembling  silver  in  color  and 
lustre,  tarnishing  slowly  in  the  air.  Its  hardness  is  interme- 
diate between  lead  and  gold.  It  is  very  malleable,  and  may  be 
hammered  out  into  foil,  the  leaves  of  which  do  not  exceed  the 
thousandth  part  of  an  inch  in  thickness.  It  has  an  unpleasant 
taste,  and  a  peculiar  odor.  It  is  soft  and  inelastic,  and,  in  small 
bars  flexible,  the  bending  being  accompanied  by  a  peculiar  sound, 
called  the  cry  of  tin,  which  has  been  attributed  to  the  sliding  of 
the  crystalline  particles  over  each  other.  Dipped  in  a  solution 
of  chloride  of  gold,  it  blackens  without  disengagement  of  gas, 
while  zinc  blackens  with  evolution  of  gas,  and  lead  remains  un- 
changed. It  fuses  at  from  440°  to  446° ;  boils  at  a  white  heat, 
and  burns  with  a  blue  flame  to  binoxide.  At  a  lower  heat  it 
forms  on  the  surface  a  dross  of  mixed  oxides. 

Its  equivalent  on  the  hydrogen  scale  is  58.82  ;  on  the  oxygen 
scale,  735.294.     Its  symbol  is  Sn,  from  the  Latin  Stannum. 

Protoxide  of  Tin,  Sn,0.  64.82. — The  protochloride  yields,  by 
precipitation  with  carbonate  of  soda,  a  hydrated  oxide  of  tin, 
which  is  best  dried  in  a  tube  through  which  a  stream  of  carbonic 
acid  gas  is  passed.  It  is  better  formed  in  the  dry  way,  by 
evaporating  to  dryness  and  then  fusing  crystallized  chloride  of 
tin,  mixing  the  residue  with  carbonate  of  soda  in  the  proportion 
of  3  to  2,  fusing  and  stirring  the  mixture  till  it  is  entirely  black, 
and  then  dissolving  out  the  resulting  chloride  of  sodium  with 
water. 

It  is  a  nearly  black  powder,  of  specific  gravity  Q.QQQ.  ■  It  is 
dissolved  in  the  acids  and  the  pure  fixed  alkalies.  Caustic 
potash,  boiled  on  it,  makes  it  crystalline,  and  dissolves  a  portion 
of  it  as  binoxide.  The  alkaline  solutions,  kept  for  any  length  of 
time,  deposit  metallic  tin,  while  deutoxide  remains  in  solution. 

Its  salts  are  generally  colorless  or  yellowish,  with  acid  reac- 
tion and  unpleasant  metallic  taste.  They  are  extremely  prone 
to  absorb  oxygen  from  the  air  and  from  other  substances  which 
yield  oxygen  readily,  and  their  use  in  calico  printing  depends 


398      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

very  much  upon  this  property.  Zinc  and  cadmium  precipitate 
the  metal  from  the  salts  except  from  the  acetate.  Sulphuretted 
hydrogen  and  hydrosulphuret  of  ammonium  throw  down  a  brown 
protosulphuret  of  tin.  This  reaction  shows  one  part  of  tin  in 
120,000  of  water.  Iodide  of  potassium  throws  down  yellow 
iodide  of  tin,  passing  occasionally  into  red.  Croconate  of  po- 
tassa  and  tincture  of  galls  give  yellow  precipitates,  other  reagents 
white. 

Binoxide  of  Tin,  ^nO^.  72.82.  Stannic  Acid. — This  oxide  is 
most  conveniently  produced  by  acting  upon  metallic  tin  with 
nitric  acid.  The  concentrated  acid  does  not  produce  any  effect, 
so  that  it  must  be  diluted  with  water.  The  hydrated  oxide, 
thus  obtained,  is  white,  and  must  be  edulcorated  with  water,  and 
heated  to  redness,  when  all  the  water  is  driven  off,  and  the  an- 
hydrous binoxide  is  left  of  a  fine  straw  yellow  color.  The  bichlo- 
ride, precipitated  by  an  alkali  and  an  alkaline  carbonate,  gives 
an  oxide  which  differs  widely  in  its  properties  from  that  which  is 
obtained  by  the  action  of  nitric  acid  on  the  metal.  Thus,  it  is 
slightly  soluble  in  nitric  acid,  while  the  other  is  insoluble ;  it  is 
soluble  in  hydrochloric  acid,  and  does  not  precipitate  when  the 
solution  is  boiled,  while  the  other  is  scarcely  soluble  in  it,  but  com- 
bines with  it  to  form  a  salt,  insoluble  in  hydrochloric  acid,  and  when 
the  acid  is  poured  off  and  the  residue  washed  with  a  little  water, 
it  dissolves,  and  again  precipitates  on  boiling  and  by  the  addi- 
tion of  hydrochloric  acid.  Both  oxides  form  salts  with  the  alka- 
lies, which  are  called  stannates.  The  hydrate  of  the  oxide 
formed  by  the  alkali  is  Sn02-l-2HO  ;  that  of  the  first  described 
oxide,  SnO^+HO. 

The  salts  are  colorless  or  yellow,  with  an  acid  reaction  when 
soluble.  Cadmium  and  zinc  throw  down  tin  in  a  dendritic  form 
from  their  solutions.  Sulphuretted  hydrogen  gives  a  yellow 
precipitate,  soluble  in  alkalies  and  sulphuret  of  ammonium.  In- 
fusion of  galls  and  ferrocyanide  of  potassium  produce  a  yellow 
jelly ;  the  other  reagents  give  generally  white  precipitates. 

Sesquioxide  of  Tin,  SnjOg. — Fuchs  obtained  this  oxide  by  treat- 
ing freshly  precipitated  hydrated  sesquioxide  of  iron  with  proto- 
chloride  of  tin.  An  exchange  of  elements  takes  place,  and  the 
sesquioxide  falls  as  a  slimy  gray  matter,  a  little  yellow  from  the 


TIN.  399 

admixture  of  iron.  Berzelius  used  a  saturated  solution  of  the 
hydrated  sesquioxide  of  iron  in  hydrochloric  acid.  Others  have 
recommended  adding  ammonia  to  the  two  solutions  before  mix- 
ing them. 

It  dries  to  yellow  translucent  grains,  soluble  in  ammonia. 
This  oxide  is  soluble  in  hydrochloric  acid,  and  then  forms  with 
terchloride  of  gold  the  purple  of  Cassius  already  described. 

Protosulphuret  of  Tin,  SnS. — Melted  tin  poured  on  its  own 
weight  of  sulphur  and  stirred  rapidly  with  a  stick  during  the 
action,  produces  this  sulphuret.  Some  tin  escapes  sulphura- 
tion  by  the  rapid  escape  of  the  more  volatile  element.  The 
mass  is  therefore  reduced  to  powder,  mixed  with  its  weight  of 
sulphur  and  projected  in  successive  portions  into  a  hot  Hessian 
crucible  and  heated  to  redness. 

It  is  a  brittle  compound,  of  a  bluish-gray,  nearly  black  color, 
and  metallic  lustre,  fusing  at  a  red  heat,  and  acquiring  a  lamel- 
lated  structure  on  cooling.  It  is  easily  reduced  to  metal  by 
heating  with  cyanide  of  potassium,  and  dissolves  in  hydrochloric 
acid  with  the  evolution  of  sulphuretted  hydrogen. 

Sesquisulphuret  of  Tin,  SnjSg. — The  protosulphuret  of  tin  in 
fine  powder  is  mixed  with  flowers  of  sulphur  and  heated  to  red- 
ness till  no  more  sulphur  escapes.  It  is  a  deep  grayish-yellow 
substance,  with  a  metallic  lustre.  Potassa  dissolves  out  bisul- 
phuret,  and  hydrochloric  acid,  protosulphuret. 

Bisulphuret  of  Tin,  ^n^^. — This  substance,  which  was  for- 
merly called  mosaic  gold,  is  obtained  by  heating  a  mixture  of  2 
parts  of  the  binoxide  of  tin,  2  of  sulphur,  and  1  of  sal  ammo- 
niac, at  a  low  red  heat  till  no  more  sulphur  is  evolved.  A  mix- 
ture of  4  parts  of  tin  filings,  3  of  sulphur,  and  2  sal  ammoniac, 
has  also  been  used.  It  is  also  obtained  by  precipitating  salts  of 
the  binoxide  of  tin  by  means  of  sulphuretted  hydrogen,  as  a 
dirty  yellow  hydrate,  which  dries  up  to  dark  yellow  hard  lumps. 

When  the  operation  has  been  successful,  the  compound  is  pro- 
cured in  gold  yellow  scales,  sometimes  in  six-sided  tables,  of  a 
metallic  lustre,  a  soft  consistence  and  a  soapy  feel.  It  is  soluble 
in  pure  potassa  and  in  its  carbonates  at  a  boiling  temperature, 
and  very  readily  in  nitro-hydrochloric  acid.     It  forms,  with  me- 


400      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

tallic  sulphurets,  double  salts,  which  have  been  called  sulpho- 
stannates. 

Phosplmret  of  Tin,  SnP. — Phosphorus,  thrown  on  melted 
tin,  gives  rise  to  a  silver  white  compound  of  a  crystalline  struc- 
ture. Rose  obtained  a  terphosphuret  by  acting  on  protochlo- 
ride  with  phosphuretted  hydrogen. 

ALLOYS   OF   TIN. 

The  effect  of  alloying  the  noble  metals  with  tin  has  already 
been  described,  as  have  also  been  the  alloys  of  this  metal  with 
copper. 

The  common  tin-plate  is  a  superficial  alloy  of  iron  and  tin 
coated  with  excess  of  tin.  The  iron  to  be  used  in  tinning  is 
very  carefully  prepared  by  heating,  scaling  off  the  oxide,  cold- 
rolling  and  pickling  in  dilute  sulphuric  acid,  till  it  gets  an  even, 
smooth,  and  perfectly  clean  surface.  It  is  then  dipped  first  in 
melted  tallow  and  afterwards  into  a  pot  of  melted  tin,  where  it 
is  allowed  to  remain  till  it  is  covered  with  a  coat  of  the  metal. 
This  is  partly  drained  off  and  partly  melted  off  in  a  second  pot 
full  of  grain  tin.  The  cleansing  is  completed  by  brushing. 
Another  dip  into  melted  tin  is  then  given  the  plates,  and  they 
are  transferred  into  a  grease-pot.  The  rim  of  tin  at  the  edge 
of  the  plate,  left  after  the  draining,  is  melted  off,  and  the  manu- 
facture is  complete. 

A  preparation  of  tin-plate  with  a  crystalline  surface  was  much 
admired  and  extensively  manufactured  some  years  since.  The 
superficial  layer  of  tin  was  dissolved  off  of  common  tin-plate  by 
means  of  dilute  acid,  and  the  exposed  surface  exhibited  these 
brilliant  spangles. 

Petvter  is  essentially  an  alloy  of  tin  and  lead,  to  which  copper 
and  antimony,  in  varying  proportions,  are  often  added.  Too 
large  a  quantity  of  lead  will  prove  highly  injurious  by  the  faci- 
lity with  which  this  metal  is  dissolved  in  vinegar  or  acescent 
wines,  and  the  poisonous  character  of  its  salts.  On  this  account, 
the  French  government,  after  appointing  Fourcroy,  Vauquelin, 
and  other  eminent  chemists,  to  examine  into  the  matter,  passed 
a  law  prohibiting  pewterers  to  use  more  than  18  per  cent,  of 
lead  in  their  wares. 


Tix.  401 

Queen's  metal  is  a  fine  variety  of  pewter,  composed  of  9  parts 
of  tin,  1  of  antimony,  1  of  bismuth,  and  1  of  lead.  Britannia 
metal  is  an  alloy,  which,  for  most  household  articles,  has  almost 
entirely  superseded  pewter.  It  is  made,  according  to  some 
authorities,  of  2  parts  of  copper,  2  of  brass,  1  of  iron,  6  of  anti- 
mony, and  89  of  tin.  It  is  a  composition,  however,  which  varies 
much  in  different  workshops.  Music  metal  is  made  of  80  parts 
of  tin  and  20  of  antimony.  Soft  solder  is  a  mixture  of  lead 
and  tin  in  the  proportion  67  to  33. 

An  amalgam  of  tin  and  mercury  is  the  compound  used  for 
silvering  mirrors.  Tinfoil  is  spread  on  a  marble  table,  and 
saturated  with  liquid  mercury.  A  large  quantity  of  the  latter 
metal  is  then  put  on,  a  clean  glass  laid  flat  upon  it,  and  pressed 
down  by  heavy  weights.  The  excess  of  mercury  being  now 
drained  off,  the  silvering  is  complete. 

HALOID  SALTS. 

ProiocJdoride  of  Tin,  SnCl. — The  anhydrous  salt  is  obtained 
by  distilling  a  mixture  of  equal  parts  of  tin  filings  and  corrosive 
sublimate,  or  by  transmitting  hydrochloric  acid  gas  over  metallic 
tin  heated  in  a  glass  tube.  It  is  a  gray  solid,  with  a  resinous 
lustre,  which  fuses  below  redness  and  sublimes  at  a  high  tem- 
perature. It  may  be  obtained  in  crystals  by  dissolving  tin  in 
hydrochloric  acid,  and  evaporating  the  solution.  It  is  necessary 
to  have  excess  of  metal  present  in  order  to  insure  the  formation 
of  a  protochloride.  The  crystals  are  long,  colorless  prisms, 
and  have  the  form  SnCl+HO. 

Dissolved  in  water,  a  cloudiness  of  greater  or  less  density 
appears,  owing  either  to  the  air  contained  in  the  water  or  to  a 
portion  of  oxychloride  of  tin.  Hydrochloric  acid  clears  the 
solution.  The  chloride  is  an  excellent  reducing  agent,  and  is 
used  in  analysis  to  reduce  the  various  metallic  oxides  to  metal, 
or  to  a  lower  degree  of  oxidation.  It  forms  double  salts  with 
the  alkalies  and  alkaline  earths. 

Sesquichloride  of   Tin,   Sn2Cl3. — This  has  been  sufiiciently 
described  under  the  head  of  Purple  of  Cassius,  in  the  chapter 
on  Gold. 
26 


402      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Bichloride  of  Tin,  SnClj. — "When  protochloride  of  tin  is 
heated  in  chlorine  gas,  or  when  a  mixture  of  8  parts  of  granu- 
lated tin  and  24  parts  of  corrosive  sublimate  is  distilled,  a 
singular  liquid,  called  the  fuming  liquor  of  Libavius,  passes 
over.  It  is  a  volatile,  colorless  liquid,  which,  when  exposed, 
emits  dense  white  fumes,  owing  to  the  moisture  it  attracts  from 
the  atmosphere.  It  remains  fluid  at  28°  below  Fahrenheit's 
zero,  and  boils  at  248°,  giving  off  a  vapor,  the  specific  gravity 
of  which,  according  to  Dumas,  is  9.1997.  With  one-third  its 
weight  of  Avater,  it  congeals  to  a  solid  mass  of  crystals ;  in  more 
water,  it  dissolves.  Solution  of  tin  in  aqua  regia  furnishes  the 
same  crystals.  It  forms  double  salts  with  the  alkaline  chlorides. 
The  i^inlc  salt  of  the  color-printer  is  one  of  these.  It  is  made 
by  adding  sal  ammoniac  to  a  solution  of  the  bichloride,  and 
crystallizing.     It  forms  several  compounds  with  sulphur. 

Bromide  of  Tin  is  a  white  soluble  salt.  The  bi-bromide, 
formed  from  tin  and  bromine,  is  fusible,  soluble  in  water,  and 
sublimes  unchanged. 

Iodide  of  Tin,  formed  when  iodine  and  tin  are  heated 
together,  is  a  brownish-red,  fusible  and  soluble  salt.  It  sub- 
limes at  a  high  heat.  It  forms  double  salts  with  the  alkaline 
iodides.  Dry  protochloride  of  tin  mixed  with  chloride  of  iodine, 
gives  rise  to  a  bichloriodide  of  tin,  which  separates  in  orange- 
colored  crystals.  The  biniodide  is  obtained  in  yellow  crystals, 
by  treating  the  hydrated  oxide  with  hydriodic  acid.  Water 
decomposes  it. 

OXYSALTS. 

Sulphate  of  Protoxide  of  Tin,  SnO,S03. — When  this  is  dis- 
solved in  sulphuric  acid,  slightly  diluted  with  water,  there  results 
a  saline  mass,  which  dissolves  in  boiling  water,  and  crystallizes 
on  cooling.  /Sulphite  of  tin  is  a  white  insoluble  powder,  which 
subsides  when  sulphite  of  soda  is  added  to  chloride  of  tin. 
Sulphurous  acid  dissolves  tin  with  the  simultaneous  formation  of 
hyposulphite  and  sulphuret. 

Sulphate  of  Binoxide  of  Tin,  Sn02,2S03. — Tin  filings,  dis- 
solved in  three  times  their  weight  of  boiling  oil  of  vitriol,  form  a 
sulphate  of  the  binoxide. 


LEAD.  403 

Nitrate  of  Tin,  SnO,N05. — This  salt  is  obtained  in  solution 
bj  treating  the  hydrated  oxide  with  cold  nitric  acid.  The  action 
of  nitric  acid  on  metallic  tin  induces  decomposition  not  only  of 
the  water,  but  of  the  acid,  as  is  proved  by  the  resulting  com- 
pound, which  contains  not  only  nitric  acid  but  ammonia  also. 
Nitrate  of  the  hinoxide  is  obtained  by  dissolving  the  hydrated 
binoxide  in  cold  nitric  acid. 

Phosphate  of  Tin,  2SnO,P05. — Phosphate  of  soda  precipitates 
this  salt  from  a  solution  of  tin.  It  is  white  and  fusible  to  a 
glass.  The  phosphite  is  a  white  powder,  which,  when  dissolved 
in  hydrochloric  acid,  is  a  most  powerful  reducing  agent. 

Borate  of  Tin  is  white,  insoluble,  and  fuses  to  an  opaque 
glass. 

The  other  salts  of  tin  are  of  no  particular  interest. 


CHAPTER    VII. 

LEAD. 

Lead  is  one  of  the  most  anciently  known  metals.  It  is  men- 
tioned in  the  Pentateuch.  In  alchemical  language  it  is  called 
saturnum,  from  its  planet,  Saturn.  The  most  common  ore  is 
Gfalena,  the  sulphuret  of  the  metal. 

metallukgy  of  lead. 

Lead  is  so  fusible  and  so  easily  reduced,  that  the  rudest  con- 
trivance will  secure  a  paying  yield  from  rich  ore.  In  the  great 
lead  region  of  the  West,  the  early  settlers  made  a  heap  of  wood 
and  ore,  set  fire  to  it,  and  collected  the  metal,  in  pigs,  in  little 
trenches  dug  in  the  earth.  It  is  usually  reduced  in  low  blast 
furnaces  or  reverberatories.  The  former  furnace  is  objectionable 
on  account  of  the  great  loss  of  lead,  amounting  sometimes  to 
nearly  half  the  metal  contained  in  an  ore.  It  is  chiefly  used 
for  the  reduction  of  rich  slags,  carbonate  of  lead,  and  litharge. 

In  the  reverberatory  furnace,  the  ore  is  spread  upon  the 


404      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

hearth  and  repeatedly  stirred,  while  a  low  red  heat  is  given  to 
the  mass.  Sulphur  slowly  hums  off,  leaving  behind  oxide  of 
lead,  while  some  of  the  sulphuret  is  oxidated  to  a  sulphate  and 
there  remains  some  unaltered  galena.  The  roasting  being  com- 
pleted, the  heat  is  raised,  and  the  lead  which  sweats  out  is 
received  in  an  iron  pot.  After  the  liquation  is  ended,  the  dross 
and  cinder  are  raked  together,  and  a  fresh  charge  operated  on 
in  the  same  manner.  The  freshly  added  galena  forms,  with  the 
oxide  of  lead,  sulphurous  acid,  metallic  lead,  and  a  portion  of 
subsulphuret,  and  the  oxide,  reacting  on  the  sulphate,  produces 
a  subsulphate. 

The  cinder  and  dross  are  now  spread  over  the  hearth ;  coal 
is  mixed  with  it,  and  a  higher  heat  applied.  The  sulphate,  oxide, 
and  sulphuret  are  partially  reduced,  and  metal  flows  out.  Lime 
is  then  added,  which  forms  sulphuret  of  lime  with  galena,  libe- 
rating metal,  and,  with  the  sulphate,  oxide  of  lead,  which  is 
reduced  by  the  coal,  while,  by  combining  with  the  silica,  it  sets 
free  any  plumbeous  oxide  which  might  have  existed  originally 
in  the  ore  as  a  silicate,  or  have  been  formed  by  the  previous 
operations.  These  processes  are  repeated  till  the  slags  are  inca- 
pable of  farther  reduction  in  this  way.  The  richer  the  ores  are, 
the  less  lead  is  lost  in  this  process.  It  sometimes  amounts  to 
but  2  per  cent.     The  rich  slags  are  reduced  in  a  blast  furnace. 

Poor  ores  and  carbonates  are  commonly  reduced  in  low  blast 
furnaces.  The  sulphurets  are  roasted  and  mixed  with  lime  and 
oxide  of  iron,  the  latter  of  which  is  essential  to  the  production 
of  a  fusible  slag.  Iron  is  often  used  for  the  direct  reduction  of 
galena,  in  either  of  the  furnaces.  It  forms  the  fusible  sulphuret 
of  iron,  and  liberates  lead.  The  favorite  method  of  dry  assay 
of  lead  ore  depends  upon  this  property  of  iron.  The  necessary 
amount  of  alkali  to  decompose  the  silicious  matters  of  the  ore, 
and  to  form  a  slag  with  them  and  the  oxides,  is  mixed  with  the 
powdered  ore,  and  beaten  down  around  iron  nails,  previously 
arranged  in  the  crucible.  Heat  is  then  applied,  and  when  the 
contents  are  in  a  state  of  fusion,  the  nails  are  lifted  one  by  one, 
rinsed  in  the  slag,  and  withdrawn.  The  metal  collects  at  the 
bottom. 


LEAD.  '  405 


LEAD  AND  ITS  NON-SALINE  COMPOUNDS. 

Lead. — Obtained  by  the  above  methods,  lead  is  always  more 
or  less  impure.  It  frequently  contains  copper,  zinc,  arsenic, 
&c.,  but  the  most  common  foreign  ingredient  is  silver.  There 
is  little  commercial  lead  free  from  this,  though  there  is  scarcely 
any  which  contains  enough  of  it  to  pay  the  cost  of  extraction, 
the  separation  of  these  two  metals  being  now  so  well  understood 
by  the  smelters.  The  most  convenient  way  of  obtaining  it  free 
from  the  common  impurities  of  copper  and  silver,  is  to  dissolve 
it  in  nitric  acid,  and  precipitate  with  excess  of  ammonia,  which 
dissolves  the  oxides  of  the  two  latter  metals,  and  to  reduce  the 
ignited  oxide  with  black  flux.  Iron  can  easily  be  separated  by 
precipitation  with  hydrochloric  acid.  The  pure  oxalate,  when 
ignited,  furnishes  a  lead  entirely  free  from  carbon. 

Lead  is  a  bluish-gray  metal,  with  a  high  lustre  when  first 
fused  or  cut,  but  rapidly  tarnishing  in  the  air.  It  crystallizes  in 
regular  octahedra.  Under  water,  it  forms  hydrated  oxides, 
which  are  soluble  in  water,  and  poisonous.  The  best  safeguard 
against  them  is  a  notable  quantity  of  sulphates  or  phosphates  in 
the  water,  which  form  with  the  lead  an  insoluble  coating  over 
the  inside  of  the  pipe,  thus  protecting  it  from  farther  oxidation. 
Persons  using  water  conveyed  through  lead  pipes,  have  been 
seriously,  and  even  fatally  affected  by  neglecting  these  precau- 
tions. The  change  is  due  to  the  air  contained  in  the  water,  as 
recently  boiled  distilled  water  has  no  effect  upon  the  metal.  , 

At  high  temperatures,  lead  absorbs  oxygen  with  great  rapidity. 
Fused  in  open  vessels,  a  gray  film  of  protoxide  and  metallic 
lead  is  formed ;  and,  when  strongly  heated,  it  is  dissipated  in 
fumes  of  protoxide.  Cold  sulphuric  acid  has  no  effect  upon  it, 
but,  when  heated,  oil  of  vitriol  acts  on  it  slowly.  It  fuses  at 
about  612°,  and  crystallizes  when  slowly  cooled. 

The  symbol  of  lead  (plumbum)  is  Pb,  its  equivalent  103.76 
on  the  hydrogen,  1294.5  on  the  oxygen  scale.  Its  specific 
gravity  is  11.33  to  11.445. 

Dinoxide  of  Lead,  PbjO. — This  is  a  dark  gray,  nearly  black 
compound,  formed  by  heating  dry  oxalate  of  lead  to  low  redness. 


406      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

The  acid  and  part  of  the  oxide  are  decomposed  into  carbonic 
acid  and  carbonic  oxide,  which  pass  over. 

Protoxide  of  Lead,  PbO. — This  is  obtained  pure  by  heating 
nitrate  of  lead  to  redness.  In  the  large  way,  it  is  made  by 
calcining  refuse  lead  at  600°,  and  as  an  incidental  product  of 
cupellation.  Fused  litharge  slowly  cooled  crystallizes.  Crys- 
tals may  also  be  obtained  from  the  solution  in  caustic  alkali. 

It  is  red  when  hot,  changing  when  cool  into  a  yellow  powder, 
with  an  orange  cast.  The  hydrated  oxide  is  white  and  crys- 
talline. 

The  salts  of  lead,  except  with  colored  acids,  are  colorless. 
They  are  precipitated  by  zinc,  as  metal,  in  an  arborescent  form, 
and  as  black  or  brown  sulphurets  by  sulphuretted  hydrogen. 
The  alkalies  throw  down  white  hydrated  oxide,  and  the  carbon- 
ates white  carbonate.  The  characteristic  tests  for  lead  are 
chromate  of  potassa  and  iodide  of  potassium,  both  of  which 
throw  down  yellow  precipitates. 

Red  Lead. — This  is  a  compound  about  the  composition  of 
which  there  has  been  much  difference  of  opinion  among  chemists. 
It  was  formerly  regarded  as  a  sesquioxide,  but  now  as  a  mixture 
of  two  oxides,  occurring  either  as  PbO-f  PbOj,  or  2Pb04-Pb02. 
Minium,  or  red  lead,  is  obtained  by  protracted  calcination  of 
the  metal.  Its  varying  color  depends  partly  on  the  mode  of 
its  preparation,  partly  on  the  admixture  of  foreign  ingredients. 

Peroxide  of  Lead,  PbOj. — This  oxide,  which  has  been  called 
plumbic  acid,  may  be  obtained  by  boiling  dilute  nitric  acid  on 
red'lead.  The  acid  dissolves  the  protoxide,  leaving  the  peroxide. 
It  unites  with  alkalies  to  form  soluble  salts. 

Red  lead  is  used  in  the  manufacture  of  glass,  and  the  peroxide 
as  an  oxidizing  agent  in  organic  chemistry,  and,  in  the  arts,  to 
make  lucifer  matches  more  inflammable.  Litharge  is  extensively 
employed  as  a  drier  in  varnishes  and  paints,  and,  by  the  apothe- 
cary, in  the  preparation  of  his  lead  plaster,  the  basis  of  all  his 
plasters. 

Sulphuret  of  Lead,  PbS. — This  substance  is  found  native  as 
galena.  It  is  formed  by  fusing  lead  with  sulphur,  or  by  pre- 
cipitating it  from  its  solutions  by  means  of  sulphuretted  hydro- 


LEAD.  407 

gen.  In  the  former  instance,  it  is  lead  gray  with  a  metallic 
lustre ;  in  the  latter,  dark  brown  or  black,  and  earthy  looking. 

It  fuses  readily,  and  at  a  high  heat  vaporizes.  By  calcination, 
part  of  the  sulphur  is  burnt  off,  and  lead  and  sulphate  of  lead 
remain.  Heated  to  whiteness  with  charcoal,  it  becomes  a  sub- 
sulphuret,  which  is  resolved  by  heat  into  galena  and  metal.  It 
is  partially  decomposed  by  steam  into  sulphuretted  hydrogen 
and  lead.  Dilute  nitric  acid  dissolves  it,  leaving  sulphur;  strong 
acid  converts  it  into  a  sulphate.  Even  dilute  acid,  at  a  high 
heat,  has  often  the  same  effect,  so  that  it  is  best  to  dissolve  the 
galena  at  the  common  temperature  of  the  air.  Iron,  ignited 
with  it,  forms  sulphuret  of  iron,  leaving  metallic  lead.  The  dry 
assay  is  made  in  this  way,  but  as  it  is  always,  even  in  the  best 
hands,  attended  by  a  loss,  it  is  best  to  rely  upon  the  humid 
assay. 

Pho^phuret  of  lead,  made  by  throwing  phosphorus  on  the 
melted  metal,  resembles  lead  in  appearance,  but  is  not  malleable. 

ALLOYS    OF   LEAD. 

Shot  are  made  of  an  alloy  of  a  large  proportion  of  lead  with 
a  little  arsenic.  One  of  the  English  patents  prescribes  a  ton  of 
the  former  to  40  pounds  of  the  latter.  Antimony  added  to 
lead,  in  the  proportion  of  1  to  4  or  5,  hardens  it,  and  consti- 
tutes the  ordinary  type-metal.  Lassaigne's  formula  (lead,  2 ; 
copper,  1 ;  antimony,  1)  is  better,  and  gives  clearer  type,  because 
copper  makes  an  expanding  alloy  with  lead.  A  small  quantity 
of  bismuth  makes  lead  tougher ;  equal  parts  of  the  two  metals 
form  a  brittle  alloy.  The  alloy  of  tin  with  lead  has  already 
been  described  in  the  chapter  on  tin.  Rose's  fusible  metal  is  2 
parts  of  bismuth,  1  part  of  lead,  and  1  part  of  tin.  A  little 
mercury  added  to  this  lowers  its  fusing  point.  Mercury  forms 
with  lead  a  solid  crystalline  amalgam,  which  floats  in  the  liquid 
mercury.  This  metal  may  be  transferred  from  one  vessel  to 
another,  by  means  of  a  lead  rod  bent  into  the  form  of  a  siphon. 
The  lead  is  penetrated  by  the  mercury,  but  remains  malleable, 
and  the  crystalline  amalgam  is  carried  over.  With  gold  and  the 
platinoid  metals,  as  well  as  with  copper,  lead  forms  brittle  alloys. 


408   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Lead  is  used  by  the  dentist  for  his  antagonizing  models  in 
making  plate-work.  At  first  it  is  not  alloyed,  but  gradually, 
during  the  process  of  working,  it  becomes  contaminated  with 
scraps  of  zinc,  bismuth,  &c.,  which  harden  it.  An  alloy  of  copper 
and  lead  would  be  preferable  to  lead  alone,  because  it  expands 
during  cooling,  and  consequently  receives  a  more  accurate  im- 
pression than  the  pure  metal.  Bismuth,  zinc,  and  antimony 
alloyed  with  lead  cause  it  to  contract  on  cooling,  and  are  there- 
fore, unless  counteracted  by  copper,  undesirable  contaminations. 

HALOID    SALTS. 

Chloride  of  Lead,  PbCl. — This  salt  is  easily  formed  by  preci- 
pitating a  solution  of  lead  in  nitric  acid,  by  means  of  hydrochlo- 
ric acid  or  a  soluble  chloride.  It  is  a  heavy  crystalline  white 
powder,  which  may  be  dissolved  in  boiling  water,  out  of  solution 
in  which  it  crystallizes,  on  cooling,  in  brilliant,  transparent, 
acicular  crystals,  often  with  a  yellowish  tinge.  In  the  air  it  is 
volatilized,  leaving  oxy chloride  of  lead  (PbO  +  PbCl).  Another 
oxychloride  is  formed  by  precipitating  subacetate  of  lead  with 
common  salt,  and  driving  off  water  by  heat.  Turner's  patent 
yellow  is  an  oxychloride  made  in  this  manner,  and  rendered 
yellow  by  fusion. 

Bromide  of  lead  (PbBr),  is  a  white  crystalline  powder,  fusible 
to  a  red  liquid,  made  either  by  double  decomposition  or  direct 
action. 

Iodide  of  lead  (Pbl)  is  obtained  in  beautiful  crystalline  scales, 
of  a  golden  yellow  color,  and  obscure  metallic  lustre,  by  precipi- 
tating a  solution  of  nitrate  of  lead  with  iodide  of  potassium. 
Dilute  solutions  give  the  finest  crystals.  A  solution  of  1  part 
of  iodide  of  potassium  in  10  of  water,  to  which  iodine  is  added 
till  it  becomes  yellowish-brown,  is  said  to  furnish  the  best  results, 
when  a  dilute  lead  solution  is  poured  into  it.  This  salt  is  soluble 
in  1,235  parts  of  cold  and  190  parts  of  boiling  water. 

Fluoride  of  lead  is  a  white,  amorphous  powder,  almost  inso- 
luble in  water,  formed  by  treating  the  oxide  or  carbonate  with 
hydrofluoric  acid. 


LEAD.  409 


OXYSALTS. 


Carbonate  of  Lead,  PbOjCOg. — This  salt  occurs  native,  both 
amorphous  and  in  beautiful  transparent  crystals.  The  artificial 
compound  is  made  by  various  formulae,  and  is  very  extensively 
used  as  a  pigment.  The  neutral  salt,  the  formula  of  which  is 
given  above,  is  obtained  by  precipitating  nitrate  of  lead  with  an 
alkaline  carbonate. 

An  imperfect  pigment,  with  little  body  and  inferior  whiteness, 
is  made  by  exposing  the  finely  divided  metal  to  air  alone,  or  air 
and  carbonic  acid,  with  constant  agitation.  Thenard's  process 
furnishes  a  paint  of  less  body  but  more  brilliant  whiteness  than 
the  ordinary  white  lead.  He  obtained  the  carbonate  by  precipi- 
tating the  basic  acetate  by  a  stream  of  carbonic  acid  gas  passed 
through  the  solution.  By  another  process,  sheets  of  lead  are 
hung  up  in  a  room,  and  exposed  to  the  conjoined  action  of 
vapor  of  vinegar,  steam,  and  carbonic  acid.  The  celebrated 
Kremnitz  white  is  made  by  suspending  sheets  of  lead  in  a  trough, 
at  the  bottom  of  which  is  a  fermenting  mass  of  wine  lees,  vinegar, 
&c.,  which  sends  up  vapors  of  vinegar  and  carbonic  acid,  thus 
corroding  the  lead.  The  high  reputation  of  this  pigment  is  due 
partly  to  the  very  careful  manner  in  which  it  is  elutriated  and 
prepared  for  the  market,  and  partly  to  the  great  purity  of  the 
metal  from  which  it  is  made. 

White  lead,  well  prepared,  has  a  soft  velvety  feel  when  rubbed 
between  the  fingers.  It  is  said  to  consist  of  globules  of  from 
0.00001  to  0.00004  of  an  inch  in  diameter.  When  prepared  in 
the  wet  way,  these  are  larger  and  of  a  more  crystalline  character. 
In  commerce,  it  is  adulterated  with  sulphate  of  baryta,  sometimes 
to  a  very  great  extent.  Some  specimens  of  commercial  white 
lead  contain  as  much  as  75  per  cent,  of  this  adulteration.  It 
has  been  thought  that,  while  the  baryta  salt  diminishes  the  body 
of  the  pigment,  its  presence  is  attended  with  some  advantages, 
among  which  is  a  diminished  tendency  to  change  of  color. 

The  following  formulae  of  diiferent  specimens  have  been  given  : 
3(PbO,C02)  and  PbO,HO  ;  2(PbO,C02)  and  PbO,ITO ;  PbO,- 
C02  4-PbO,HO.  The  last  formula  represents  the  better  class 
of  commercial  white  lead. 


410      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Nitrate  of  Lead^  PbO,NOj. — When  lead  is  heated  with  dilute 
nitric  acid  it  is  rapidly  taken  up,  and  the  solution,  after  evapo- 
ration and  cooling,  lets  fall  crystals  belonging  to  the  regular 
system.  It  is  soluble  in  ■water,  less  so  in  nitric  acid,  not  at  all 
in  alcohol. 

Sulphate  of  Lead,  PbO,S03. — Sulphuric  acid  acts  upon  lead 
with  such  difficulty  that  this  metal  is  universally  used  by  the 
manufacturers  of  oil  of  vitriol  in  the  construction  of  their  con- 
densing chambers  and  concentration-vats.  It  is  not,  however, 
wholly  insoluble  in  this  acid,  as  little  or  no  commercial  oil  of 
vitriol  can  be  found  destitute  of  a  notable  quantity  of  the  salt. 
It  is  best  obtained  by  precipitating  the  nitrate  or  acetate  of  lead 
with  sulphuric  acid  or  a  soluble  sulphate. 

It  is  a  white  powder,  fusible  without  decomposition,  but  readily 
decomposed  by  ignition  with  charcoal  or  silica.  It  is  scarcely 
soluble  in  water,  but  dissolves  in  small  quantity  in  water  acidu- 
lated with  sulphuric  acid,  and  more  freely  in  oil  of  vitriol.  It  is 
soluble  in  ammoniacal  salts,  especially  the  sulphate,  with  which 
it  forms  a  double  salt. 

Pliosphate  of  Lead. — There  are  two  phosphates  of  lead  formed 
by  precipitating  solutions  of  lead  salts  with  the  common  phos- 
phate of  soda.  One  of  these  is  obtained  from  the  acetate,  the 
other  from  the  chloride  of  lead.  Both  are  sometimes  formed 
together.  The  latter  fuses  into  a  yellow  bead,  which,  on  cooling, 
acquires  crystalline  facets. 

Acetates  of  Lead. — There  are  four  acetates  of  lead.  The 
neutral  acetate  (PbO,A,3ag)  is  obtained  by  dissolving  the  oxide 
or  carbonate  in  excess  of  acid  and  crystallizing.  When  the 
solution  is  rapidly  cooled,  needles  are  deposited.  By  slower  re- 
frigeration, white  right-rhombic  prisms,  with  dihedral  summits, 
are  obtained.  It  is  the  salt  known  as  sugar  of  lead,  and  is 
largely  used  in  medicine  and  in  the  arts.  The  sesquibasic  ace- 
tate (3PbO,2A)  is  made  by  gently  heating  the  dry  neutral  ace- 
tate in  a  porcelain  capsule,  till  the  fused  salt  congeals  to  a  po- 
rous white  mass.  This  is  then  dissolved  in  water,  the  solu- 
tion concentrated  to  the  consistence  of  syrup  and  set  aside 
to  cool,  when  pearly,  six-sided  tables  separate.  The  trihasio 
acetate  (3PbO,A)  is  deposited  in  long  silky  needles  from  a  cold 


LEAD.  411 

saturated  solution  of  neutral  acetate  whicli  has  been  mixed 
with  one-fifth  of  its  volume  of  water  of  ammonia.  The  sex- 
hasic  acetate  (6PbO,A)  is  a  white  powder,  which,  under  the 
microscope,  is  found  to  be  crystalline.  It  is  obtained  by  super- 
saturating any  of  the  acetates  with  ammonia.  Boiling  water  dis- 
solves it  and  lets  it  fall,  on  cooling,  in  brilliant,  feathery  crystals. 
The  basic  acetates  are  used  in  dyeing,  and  in  the  manufacture  of 
chrome  yellow. 

Borate  of  Lead. — Lead  forms,  with  boracic  acid,  glasses  of  va- 
rious degrees  of  hardness  and  solubility.  A  very  soft  yellow 
glass  is  obtained  by  fusing  together  112  parts  of  oxide  of  lead 
and  24  of  boracic  acid.  A  hard,  transparent,  and  highly  refract- 
ing glass  is  made  from  the  same  quantity  of  litharge  and  72 
parts  of  the  acid.     PbO,2Bo3  is  slightly  soluble  in  water. 

Chromate  of  Lead,  PbO,Cu03.  164.  Chrome  Yelloiv.—This 
is  a  powder  formed  in  various  ways,  but  usually  by  precipitating  a 
solution  of  crystallized  acetate  or  nitrate  of  lead  by  chromate 
or  bichromate  of  potassa.  It  is  a  fine  yellow  pigment,  insoluble 
in  water,  but  soluble  in  potassa,  with  a  formation  of  the  basic 
chromate.  Various  paler  lemon  tints  are  obtained  by  mixing 
sulphuric  acid,  in  different  proportions,  with  the  chromate  of 
potassa  before  the  precipitation.  They  depend  upon  the  admix- 
ture of  the  white  sulphate  of  lead,  which  weakens  the  yellow. 

Basic  Chromate  of  Lead,  2PbO,Cr03.  276.  Chrome  Orange. — 
This  is  easily  made  by  boiling  the  yellow  chromate  with  weak 
aqua  potassse.  Hayes  obtained  it  in  orange  yellow  needles,  by 
treating  a  solution  of  litharge  in  caustic  soda  with  chromate  of 
potassa,  in  an  atmosphere  charged  with  carbonic  acid.  Nobler 
and  Liebig  made  a  fine  vermilion-colored  basic  chromate,  by 
projecting  the  yellow  chromate  in  nitre  fused  at  a  low  heat,  till 
the  latter  salt  is  almost  entirely  decomposed.  The  crucible  is 
allowed  to  stand  till  the  dense  basic  salt  subsides,  when  the 
fluid  part  is  poured  off,  and  the  basic  salt  washed  rapidly  with 
water.  Chrome  orange  is  also  used  as  a  pigment,  but  is  more 
liable  to  fade  in  the  air  than  the  yellow. 

Silicate  of  Lead  is  the  basis  of  flint  glass  and  artificial  gems. 
Strass  is  said  to  be  KO,Si03-l-3(PbO,Si03). 


412  CHEMISTRY  OF  METALS  AXD  EARTHS  USED  BY  THE  DENTIST. 


CHAPTER   VIII. 

BISMUTH. 

Bismuth  was  first  shown,  by  G.  Agricola,  to  be  distinct  from 
lead,  in  1546.  It  is  occasionally  found  native,  but  most  com- 
monly combined  with  the  ores  of  other  metals,  with  sulphur, 
selenium,  tellurium,  and  silica.  In  Saxony,  where  it  is  princi- 
pally worked,  it  is  obtained  as  a  secondary  product  from  arseni- 
cal cobalt. 

At  Schneeberg,  in  Saxony,  it  is  sweated  out  of  the  ore  in 
peculiar  eliquation  furnaces.  The  broken  ore  is  put  into  earthen 
pipes  which  have  holes  in  their  under  side,  to  allow  the  melted 
metal  to  drip  out  into  hot  iron  pans.  These  contain  coal-dust, 
which  is  floated  up  by  the  melted  metal,  and  forms  a  film  on  its 
surface,  protecting  it  from  oxidation.  When  the  pans  are  nearly 
full,  the  metal  is  lifted  out  and  cast  in  bars. 

Bismuth  thus  obtained  resembles  the  pure  metal,  but  is  largely 
contaminated  with  arsenic,  sulphur,  iron,  &c. 

bismuth    and    its    NON- SALINE    COMPOUNDS. 

Bismuth. — The  commercial  metal  is  best  purified  by  dissolving 
in  pure  nitric  acid,  filtering  or  decanting,  to  get  a  clear  solution, 
precipitating  the'subnitrate  by  the  addition  of  water,  digesting 
the  precipitate  with  caustic  potassa  to  extract  arsenious  acid, 
and  reducing  the  residue  with  black  flux  at  a  low  red  heat. 

It  crystallizes  in  octahedra  and  cubes,  with  distinct  cleav- 
age. It  is  best  crystallized  by  heating  the  commercial  metal  in 
a  crucible  with  a  little  nitre,  to  the  fusion  point  of  the  salt.  More 
nitre,  in  small  quantities,  is  added  from  time  to  time,  the  whole 
being  constantly  stirred.  Test  pieces  are  taken  out  repeatedly 
for  examination.  At  first,  they  are  of  a  violet  or  rose  color, 
which  disappears  on  cooling.  When  this  tint  disappears  and  is 
replaced  by  a  green  or  yellow,  which  is  permanent,  the  metal  is 


BISMUTH.  41B 

sufficiently  purified.  It  is  then  to  be  poured  into  a  heated  cru- 
cible, cooled  till  about  one-half  congealed,  the  surface  broken, 
and  the  remaining  liquid  metal  poured  out. 

It  is  a  soft  metal,  with  but  little  sonorous  property,  brittle, 
but  capable  of  some  degree  of  extension  by  careful  hammering. 
Its  malleability  is  increased  by  heating.  It  is  reddish-white, 
with  some  lustre,  and  undergoes  little  change  in  the  air  at  com- 
mon temperatures,  but,  when  fused  in  open  vessels,  becomes 
coated  with  a  gray  film  of  mixed  metal  and  oxide.  It  fuses  at 
about  500°,  and  is  said  to  expand  on  cooling.  At  a  high  heat 
it  may  be  distilled  in  close  vessels,  being  condensed,  after  sub- 
limation, in  laminge.  It  is  soluble  in  nitric  acid  and  aqua  regia, 
but  the  process  is  immediately  arrested  by  laying  a  piece  of 
platinum  on  the  metallic  bismuth. 

The  specific  gravity  of  pure  bismuth  is  9.654  according  to 
some  authors,  9.799  according  to  others.  The  symbol  of  bis- 
muth is  Bi.  Its  equivalent  is  variously  stated,  as  the  opinions 
of  chemists  vary,  in  reference  to  the  constitution  of  the  most 
powerful  base.  This  was  formerly  regarded  as  a  sesquioxide 
(Bi203),  and,  the  percentage  being  about  89.87  bismuth,  and 
10.13  oxygen,  the  combining  number  was  stated  at  106.5. 
After  a  time,  however,  an  analogy  was  discovered  between  the 
salts  of  bismuth  and  those  of  magnesia.  The  formula  was 
consequently  altered  to  BiO,  and  the  equivalent  to  71.  Again, 
the  resemblance  between  compounds  of  bismuth  and  antimony, 
and  the  analogy  between  the  specific  volumes  of  bismuth  and  tin, 
led  to  the  adoption  of  BiOj  as  the  formula,  and  consequently 
213  as  the  atomic  weight  of  the  metal. 

Suboxide  of  Bismuth. — This  oxide  is  formed  when  bismuth  is 
melted  in  the  air,  and  kept  fused  for  a  long  time,  or  when  the 
basic  nitrate  is  digested  with  excess  of  protochloride  of  tin. 
It  is  reddish-brown  or  black,  according  to  the  mode  of  prepara- 
tion. 

Oxide  of  Bismuth. — Bismuth,  heated  in  the  air,  burns  with 
a  pale  blue  flame  to  oxide  or  flower  of  bismuth.  In  the  dry  way, 
this  oxide  is  prepared  by  the  thorough  oxidation  of  fused  bis- 
muth by  constant  stirring,  or  by  igniting  the  carbonate  or 
nitrate.     Thus   obtained,  it  is  a   yellow  powder.     It  may  be 


414      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

procured  in  shining  yellow  needles  by  fusing  caustic  potassa 
with  excess  of  the  oxide,  and  boiling  with  a  concentrated  potash 
or  soda  lye.  The  hydrate  is  white,  and  is  made  by  double 
decomposition. 

Bismuthio  Acid. — Some  experiments  are  recorded  which  go 
to  show  that  there  are  other  oxides,  some  of  which  appear  to 
have  slight  acid  properties.  By  fusing  the  oxide  with  caustic 
soda,  boiling  the  fused  mass  with  soda  lye,  and  washing  with 
nitric  acid  and  water,  a  brown  oxide  is  obtained,  which  yields 
a  yellow  oxide  when  fused  with  caustic  potash.  The  yellow 
oxide,  treated  with  nitric  acid,  forms  another  of  a  reddish-brown 
tint. 

SuIjyJiuret  of  Bismuth. — The  tersulphuret  occurs  native  as  Bis- 
muth Glance.  It  may  be  made  by  fusing  the  metal  and  sulphur 
together,  or  by  precipitating  bismuth  with  sulphuretted  hydro- 
gen. It  is  either  lead  gray  or  brown,  according  to  the  manner 
in  which  it  is  prepared. 

Phosphuret  of  Bismuth. — Phosphorus  has  not  a  very  strong 
affinity  for  bismuth.  It  combines  with  it,  however,  in  the  dry 
way,  forming  a  foliated  compound.  It  precipitates  from  the 
nitrate  a  black  phosphuret,  which  loses  all  its  phosphorus  by 
distillation. 

ALLOYS  OF  BISMUTH. 

Bismuth  increases  the  fusibility  of  an  alloy,  and,  if  added  in 
sufficient  quantity,  usually  confers  on  the  compound  the  pro- 
perty of  expansion.  The  dentist  uses  it  to  alloy  his  zinc  for 
moulds,  on  account  of  the  two  properties  above-mentioned. 

It  alloys  readily  with  potassium  and  sodium.  The  former 
mixture  may  be  obtained  by  fusing  bismuth  with  bitartrate  of 
potassa.  These  alloys  are  readily  oxidated  by  water,  hydrogen 
being  given  off  and  bismuth  left  in  a  pulverulent  form. 

Bismuth  does  not  combine  readily  with  arsenic,  but  with  anti- 
mony it  unites  in  every  proportion,  and  when  the  alloy  contains 
33  or  more  parts  of  bismuth  in  the  hundred  it  expands  on 
cooling.     With  cojjper,  it  forms  a  red  and  brittle  compound. 


BISMUTH.  415 


SALTS. 


The  salts  of  bismuth  are  easily  obtained  by  solution  of  the 
oxide  in  liquid  acid,  by  double  decomposition,  and  by  decompo- 
sition through  the  agency  of  water.  All  the  soluble  salts  form 
basic  salts  on  the  addition  of  water  to  their  solutions,  unless  the 
latter  contain  great  excess  of  acid.  Metallic  bismuth  is  rapidly 
precipitated  from  them  by  zinc  and  cadmium,  more  slowly  by 
tin,  iron,  and  lead,  and  by  copper  only  from  a  warm  solution. 
Alkaline  carbonates  throw  down  a  carbonate ;  earthy  carbonates 
a  hydrated  oxide.  Sulphuretted  hydrogen  and  hydrosulphurets 
precipitate  all  the  bismuth  as  a  brownish-black  sulphuret. 

Chloride  of  Bismuth. — This  salt,  which  has  also  been  called 
butter  of  bismuth,  is  formed  with  evolution  of  light  and  heat, 
when  finely  divided  bismuth  is  introduced  into  chlorine  gas. 
The  common  mode  of  preparation  is  to  distil  bismuth  with  cor- 
rosive sublimate  or  to  dissolve  it  in  strong  hydrochloric  acid. 
It  is  brownish  or  grayish-white,  and,  when  formed  by  the  last  pro- 
cess, crystallizes  in  prisms.  It  fuses  readily  to  an  oily  liquid,  and 
at  a  gentle  heat  is  volatilized.  Water  decomposes  it,  throwing 
down  an  oxychloride.  This  is  white,  crystalline,  fusible,  and 
easily  decomposed.  The  chloride  also  forms  double  salts  with 
the  alkaline  chlorides. 

Bromide  of  Bismuth  is  formed  by  the  direct  action  of  heated 
bromine  upon  finely-divided  metallic  bismuth.  It  is  a  steel  gray 
compound,  resembling  iodine.  At  392°,  it  fuses  to  a  hyacinth 
red  liquid,  but  regains  its  original  appearance  on  cooling. 
Exposed  to  the  air,  it  rapidly  absorbs  moisture,  and  acquires  a 
fine  sulphur  yellow  color.  Water  decomposes  it  into  hydrochloric 
acid  and  oxide  of  bismuth. 

Iodide  of  Bismuth  is  a  brown  crystalline  salt,  obtained  by 
double  decomposition.  The  subiodide  is  volatile,  subliming, 
before  fusion,  in  scales  of  a  metallic  lustre.  It  is  made  by 
heating  together  equal  parts  of  bismuth  and  iodine.  An  oxy- 
iodide  is  made  by  boiling  the  iodide  in  water. 

Sulphate  of  Bismuth. — This  salt  is  obtained  by  dissolving  the 
metal  in  sulphuric  acid  and  evaporating  to  dryness.     Ignited  in 


416      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

hydrogen,  it  leaves  pure  bismuth.  Water  resolves  it  into  sul- 
phuric acid  and  an  insoluble  basic  sulphate. 

Nitrate  of  Bismuth. — The  neutral  salt  is  made  by  dissolving 
bismuth  in  warm  nitric  acid  and  crystallizing.  The  action  is 
so  violent  that  the  temperature  rises  to  actual  ignition  when 
finely  divided  bismuth  and  fuming  nitric  acid  are  used.  The 
crystals  are  transparent  and  colorless  prisms.  Water  forms  with 
it  the  basic  salt  known  by  the  various  names  of  pearl  white,  tris- 
nitrate,  subnitrate,  and  magistery  of  bismuth.  It  is  a  pure  white, 
pearly,  loose  powder,  composed  of  crystalline  scales  invisible  to 
the  unaided  eye.  Sometimes  minute  needles  are  mingled  with 
the  scales.  The  greatest  yield  is  obtained  by  adding  2,400  parts 
of  boiling  water  to  100  parts  of  the  crystals.  In  this  way  45.5 
parts  of  basic  salt  are  produced. 

The  salt  was  used  as  a  cosmetic,  but  has  gone  out  of  vogue 
on  account  of  its  growing  dark  by  exposure  to  the  air  and 
blackening  in  the  presence  of  sulphuretted  hydrogen.  It  is 
employed  in  medicine,  and  is  a  favorite  remedy  with  many  phy- 
sicians in  cases  of  indigestion,  especially  when  accompanied  by 
much  gastric  pain.  Some  regard  it  as  a  local  anaesthetic  to  the 
stomach. 

Phosphate  of  bismuth  is  a  white  insoluble  powder,  fusible  to 
a  white  enamel.  The  bibasic  phosphate  is  formed  by  double 
decomposition  with  pyrophosphate  of  soda.  The  monobasic 
phosphate  is  obtained  by  adding  metaphosphoric  acid  and  ammo- 
nia to  a  salt  of  bismuth. 

We  pass  over  the  remaining  salts  of  this  metal. 


CHAPTER   IX. 

PLATINUM. 

This  metal  was  mentioned  by  Ulloa  in  1741,  but  does  not 
appear  to  have  been  attended  to  in  Europe  till  1748.  It  was 
first  sent  over  from  South  America  as  platinum  sand,  and  brought 
into  the  market  under  the  name  of  white  gold.     The  Spaniards, 


PLATINUM.  417 

however,  soon  gave  it  the  name  of  platina  (which  is  a  diminutive 
of  plata,  silver),  from  its  resemblance  in  color  to  that  metal. 

It  is  rarely,  if  ever,  found  pure,  being  alloyed  with  several 
other  metals,  the  most  common  of  which  are  those  commonly 
called  the  platinoid  metals,  palladium,  iridium,  osmium,  rho- 
dium, and  ruthenium.  It  has  also  been  found  in  company  with 
gold,  silver,  iron,  manganese,  copper,  lead,  titanium,  and  chro- 
mium. 

It  occurs  in  the  form  of  grains,  which  are  usually  flattened, 
and  resemble  somewhat  the  gold  pepitas.  They  are  generally 
smaller  than  flaxseed,  though  occasionally  found  as  large  as 
peas.  A  piece  brought  by  Humboldt  from  Choco,  in  Peru,  and 
by  him  presented  to  the  Cabinet  at  Berlin,  is  larger  than  a 
pigeon's  egg,  and  weighs  1088.6  grains.  In  the  Royal  Museum 
of  Madrid  is  another,  larger  than  a  turkey's  egg,  and  weighing 
fully  2  pounds  troy.  But  the  largest  masses  have  come  from 
Russia.  One  of  these,  discovered  in  1824  at  Nischne-Tagilsk, 
weighed  10  pounds ;  and  another,  found  in  1830,  weighed  fully 
18  pounds  avoirdupois. 

The  color  of  the  grains  of  native  platinum  is  generally  a 
grayish-white,  like  tarnished  steel.  The  rougher  particles  have 
often  earthy  and  ferruginous  matters  clinging  to  them.  The 
black  oxide  of  iron  is  a  very  common  contamination.  Their 
specific  gravity  is  much  lower  than  that  of  the  metal,  varying 
from  15  in  the  smaller  to  18.94  in  the  larger  specimens.  Among 
them  are  found,  in  very  considerable  quantity,  the  excessively 
hard,  tough,  flat,  silvery  spangles  of  iridosmin. 

Of  the  localities  of  platinum,  one  of  the  most  important  is  the 
western  slope  of  the  Andes,  in  New  Granada  and  Peru.  The 
gold  washings  of  these  regions  contain  this  metal.  The  deposit 
is  found  in  alluvial  ground  at  the  depth  of  about  20  feet. 
Formerly,  the  metals  were  separated  by  picking ;  and,  when  it 
was  supposed  that  the  platinum  might  be  used  to  debase  the 
gold,  great  quantities  of  it  were  thrown  into  the  rivers.  Brazil 
is  another  important  platinum  region.  The  metal  is  found  there 
also  mixed  with  small  particles  of  gold,  but  without  the  magnetic 
iron-sand  or  small  zircons  which  accompany  the  Peruvian  ore. 
It  is  mixed  with  fibrous  and  radiated  grains  of  native  palladium, 
27 


418      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

and  the  platinum  granules  themselves  are  remarkably  spongy 
and  brilliant.  In  St.  Domingo,  this  metal  is  found  in  the  fer- 
ruginous quartzose  sand  of  the  river  Jacky,  near  the  mountains 
of  Sibao.  This  native  platinum  contains  nearly  all  the  associated 
metals  already  named. 

The  most  important  source  of  platinum,  however,  is  the  Ural 
range  of  mountains  in  the  empire  of  Russia.  The  geological 
conformation  of  the  region  producing  it  corresponds  very  much 
with  that  of  the  platinum  region  of  South  America.  It  is  mingled 
with  gold  in  sands  which  are  almost  all  superficial,  covering  an 
argillaceous  soil,  and  including  debris  of  dolerites,  protoxide  of 
iron,  corundum,  &c.  The  grains  are  thicker,  and  not  so  flat  as 
the  Peruvian  ;  they  are  round,  less  brilliant,  and  more  lead- 
colored.  The  sand  is  manifestly  the  result  of  the  wearing  away 
of  the  surrounding  rocks.  Large  quantities  of  iridosmin  are 
found  in  it. 

Though  usually  contained  in  alluvial  washings,  Boussingault 
discovered  it  in  a  sienitic  rock  associated  with  gold ;  and  Vau- 
quelin  found  10  per  cent,  of  it  in  an  argentiferous  copper  ore, 
said  to  have  come  from  Guadal  Canal,  in  Spain. 

PREPARATION   OF    PLATINUM. 

The  ore  is  first  thoroughly  washed,  in  order  to  free  it  as  much 
as  possible  from  earthy  impurities.  A  magnet  is  then  passed  over 
it  to  remove  the  magnetic  iron  ore  that  may  be  present.  The 
remainder  of  the  iron  is  dissolved  out  by  means  of  dilute  hy- 
drochloric acid. 

The  purified  grains  are  now  introduced  into  a  tubulated  retort, 
connected  with  a  cooled  receiver.  Hydrochloric  acid  is  then 
poured  over  them,  and  heat  is  applied ;  nitric  acid  being  gra- 
dually added,  not  in  excess,  lest  iridium  should  be  precipitated. 
Distillation  is  carried  on  till  the  residue  in  the  retort  has  acquired 
the  consistence  of  a  syrup,  when  it  is  dissolved  in  hot  water, 
mixed  with  the  distillate,  and  the  whole  distilled  anew.  What 
comes  over  is  colorless  (if  not,  it  is  distilled  till  it  is  so),  and 
contains  osmic  acid.  It  is  neutralized  by  ammonia,  or  milk  of 
lime,  charged  with  sulphuretted  hydrogen,  and  allowed  to  stand 
until  the  sulphuret  of  osmium  subsides,  for  which  several  days 


PLATINUM.  419 

are  required.  The  addition  of  the  alkalies  is  designed  to  prevent 
the  decomposition  of  the  sulphuretted  hydrogen.  The  precipi- 
tation should  be  made  in  a  close>ly-stopped  flask,  of  such  a  size 
as  to  be  nearly  filled  -with  the  solution.  The  resulting  sulphuret 
of  osmium  contains,  according  to  Berzelius,  from  50  to  52  per 
cent,  of  metal.  This  process  depends  upon  the  volatility  of 
osmic  acid,  which  is  formed  by  the  continuous  decomposition  of 
the  chloride  of  osmium. 

The  residue  may  be  again  treated  with  aqua  regia.  It  must 
be  boiled  to  expel  the  excess  of  chlorine,  generated  by  the  de- 
composition of  chloride  of  palladium,  filtered  and  precipitated  by 
an  excess  of  saturated  watery  solution  of  chloride  of  potassium, 
which  throws  down  the  double  chlorides  of  platinum,  iridium,  \ 
and  ruthenium.  The  precipitate  must  now  be  washed  with  a 
solution  of  chloride  of  potassium,  and  the  double  chloride  of 
ruthenium  extracted  by  alcohol. 

The  double  chlorides  of  platinum  and  iridium  are  dried,  mixed 
with  twice  their  weight  of  carbonate  of  potassa,  and  heated  nearly 
to  fusion,  in  order  to  decompose  the  double  salts,  and  oxidate 
the  rhodium  and  iridium.  It  is  then  washed,  first  with  water, 
afterwards  with  dilute  hydrochloric  acid,  and  finally  with  water 
on  a  filter.  The  residue  is  then  treated  with  slightly  warm 
dilute  aqua  regia  till  nothing  more  is  taken  up.  The  fluid  is 
decanted,  and  concentrated  acid  poured  upon  the  residue  ;  the 
solutions  mixed  and  evaporated  with  chloride  of  sodium.  The 
object  of  adding  this  is  to  prevent  the  formation  of  proto-chlo- 
ride  of  platinum.  The  soluble  double  chloride  is  now  extracted 
with  water,  and  the  residue,  which  is  oxide  of  iridium,  well 
washed  upon  a  filter.  The  same  process  is  used  with  the  solu- 
tions so  long  as  they  contain  iridium.  The  pure  platinum  solu- 
tions are  precipitated  with  sal  ammoniac,  which  throws  down  a 
brilliant  yellow  double  salt  if  no  foreign  metal  be  present.  The 
precipitate,  heated  to  ignition  and  washed,  is  pure  platinum.  The 
solutions  to  which  the  sal  ammoniac  has  been  added  are  also  evapo- 
rated and  ignited,  to  obtain  the  platinum  that  may  have  escaped 
precipitation.  The  oxide  of  iridium^  ignited  in  a  stream  of 
hydrogen  gas,  yields  the  metal. 

The  liquid  from  which  the  double  chlorides  were  separated, 


420     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

contains  palladium,  rhodium,  copper,  and  iron,  with  some  plati- 
num and  iridium.  It  is  acidulated  with  hydrochloric  acid,  and 
precipitated  by  means  of  metallic  zinc  or  iron.  The  precipitate 
is  redissolved  in  aqua  regia,  and  exactly  neutralized  with  car- 
bonate of  soda.  Cyanide  of  mercury  is  added,  which  throws 
down  cyanide  of  palladium,  mixed  with  some  copper ;  this  is 
again  dissolved  in  aqua  regia,  and  chloride  of  potassium  added. 
The  solution  is  evaporated  to  dryness,  with  repeated  addition  of 
aqua  regia,  and  the  dry  residue  powdered.  The  double  chloride 
of  copper  and  potassium  being  extracted  by  means  of  alcohol, 
the  palladio-chloride  of  potassium  remains.  This,  ignited  with 
sal  ammoniac  and  washed,  leaves  pure  palladium. 

The  liquid  which  remains  after  filtering  off  the  precipitated 
cyanides  in  the  last  process,  is  evaporated  to  dryness  with  hy- 
drochloric acid,  to  expel  hydrocyanic  acid.  The  dried  mass  is 
ignited  with  bisulphate  of  potassa,  and  the  potash  salts  and  the 
copper  are  dissolved  out  with  water  and  hydrochloric  acid.  The 
residue  is  heated  with  bisulphate  of  potassa  till  it  begins  to  con- 
geal. This  takes  up  the  oxide  of  rhodium.  The  salt  is  then 
treated  with  boiling  water,  and  the  red  or  black  solution  evapo- 
rated. The  same  process  must  be  repeated  so  long  as  the  salt 
is  colored.  To  avoid  the  trouble  of  adding  much  bisulphate  of 
potash,  weighed  quantities  of  sulphuric  acid  may  be  added,  from 
time  to  time,  to  the  decomposed  salt.  The  residue  from  this 
is  ignited  with  carbonate  of  potassa  and  washed.  Oxide  of 
rhodium  remains. 

The  residue  of  the  first  treatment  with  aqua  regia  contains 
iridium,  osmium,  and  iridosmin.  Wohler  mixed  this  with  com- 
mon salt,  introduced  it  into  a  green  glass  tube,  and,  while  heated 
to  low  redness,  passed  a  stream  of  chlorine  -gas  over  it.  The 
tube  communicated  with  a  tubulated  receiver  containing  ammo- 
nia, and  the  operation  was  continued  till  the  chlorine  entered 
the  ammoniacal  solution  in  considerable  quantity.  Two  double 
salts  are  thus  formed,  the  iridio-chloride  and  the  osmio-chloride 
of  sodium.  The  latter  salt  decomposes  in  the  presence  of  water 
into  osmium,  hydrochloric  acid,  and  osmic  acid.  The  latter 
passes  over  into  the  receiver,  while  the  two  former  combine  to 
be  again  decomposed.  The  contents  of  the  tube  are  digested  in 
water,  and  the  brown  solution  submitted  to  a  second  distillation, 


PLATINUM.  421 

to  obtain  more  osmic  acid.  The  remainder  is  evaporated  in  an 
open  dish,  with  the  occasional  addition  of  carbonate  of  soda. 
The  dry  bUick  mass  is  feebly  ignited  in  a  Hessian  crucible. 
When  cold,  the  saline  matter  is  removed  by  boiling  water,  and 
there  remains  a  black  powder  of  oxide  of  iridium,  which  may  be 
reduced  to  metal  by  hydrogen  gas. 

Ruthenium  is  separated  by  fusing  equal  parts  of  potassa  and 
chlorate  of  potassa  in  an  iron  crucible,  and  adding  6  parts  of  iri- 
dosmin.  The  resulting  black  mass  is  washed  with  warm  water, 
leaving  behind  oxide  of  iridium  and  unaltered  iridosmin.  The 
yellow  water  which  has  been  poured  off  from  the  washing  is 
exactly  saturated  with  nitric  acid,  oxide  of  ruthenium  falls,  and 
osmiate  of  potassa  remains  in  solution.* 

..The  Russian  process  is  more  simple  than  the  above  (which  is. 
a  modification  of  Berzelius's  process  of  analysis),  though  it  does 
not  accomplish  as  perfect  a  separation  of  all  the  platinoid  metals. 
The  ore  is  treated  with  aqua  regia  in  open  vessels  on  a  sand- 
bath,  arranged  under  a  glazed  dome  with  a  ventilating  chimney, 
so  that  all  the  vapors  are  carried  out  of  the  laboratory.  Heat  is 
applied  for  eight  or  ten  hours,  till  the  cessation  of  red  fumes  proves 
that  all  the  nitric  acid  is  decomposed.  The  supernatant  solu- 
tion is  decanted,  and  the  residue  again  treated  with  aqua  regia 
till  all  is  taken  up.  The  acid  used  is  composed  of  1  part  nitric 
and  3  hydrochloric  acid.  It  requires,  of  acid,  from  ten  to  fifteen 
times  the  weight  of  the  ore  to  dissolve  it. 

The  solutions  thus  made  are  all  very  acid,  to  prevent  the  pre- 
cipitation of  iridium,  when  water  of  ammonia  is  added.  This  is 
the  next  process,  and  the  ammonio-chloride  of  platinum  having 
settled,  the  supernatant  liquid  is  poured  oiF,  and  the  precipitate 
well  washed,  dried,  and  calcined  in  platinum  crucibles. 

The  mother  waters  and  washings  are  treated  separately.  The 
first  being  evaporated  to  one-sixth  of  their  bulk,  let  fall  the  iri- 
dium as  a  dark  purple  powder,  occasionally  crystallized  in  octa- 
hedra.  The  washings  are  evaporated  to  dryness,  and  the  residue 
treated  like  fresh  ore,  but  the  platinum  obtained  from  them 
needs  a  second  purification. 

The  result  of  the  ignition  of  the  platino-chloride  of  ammonium 

*  Booth's  Cyclopaedia  of  Chemistry. 


422   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

is  spongy  platinum.  This  is  beaten  with  water  in  bronze  mor- 
tars, sifted  through  fine  sieves,  and  the  powder  driven  forcibly 
into  a  cylinder  by  means  of  a  powerful  coining  press.  It  is 
then  turned  out  of  the  mould  and  baked  for  36  hours  in  a  porce- 
lain kiln,  after  which  it  may  be  forged.  It  contracts  in  volume 
from  one-sixth  to  one-fifth  during  the  calcination.  In  very 
large  quantities,  this  process  is  somewhat  modified.  The  block 
obtained  by  compression  is  heated  in  a  smith's  forge  at  the  angle 
of  meeting  of  two  tuyeres.  When  it  has  reached  the  welding 
point,  which  is  intense  whiteness,  a  heavy  drop,  very  much  like 
the  hammer  of  a  pile-driving  machine,  is  let  fall  upon  it.  It  is 
reheated,  and  receives  a  fresh  blow  every  twenty  minutes,  and  in 
a  week  or  ten  days  its  consolidation  is  completed. 

These  large  masses  are  used  for  the  great  pans  employed  in 
making  pure,  concentrated  sulphuric  acid,  and  the  vessels  for 
parting  by  means  of  that  acid. 

METALLURGY   OF   THE   ALLOYS   OF   PLATINUM. 

Crold  and  Platinum. — Gold  is  frequently  alloyed  with  pla- 
tinum, either  by  design  or  accident.  The  great  weight  of  plati- 
num and  its  lower  value  than  gold,*  furnish  sufficient  induce- 
ments for  the  fraudulent  admixture  of  the  two  metals.  Oftener, 
however,  this  alloy  is  the  result  of  accident.  Platinum,  though 
wholly  unalterable  by  fire  in  its  pure  state,  is,  nevertheless,  ca- 
pable of  forming  a  fusible  alloy  with  a  fusible  metal.  The 
mechanical  dentist's  scraps  are  just  in  the  condition  to  form  this 
alloy,  because  he  uses  both  gold  and  platinum,  and  has  just 
enough  of  the  more  fusible  metals  to  bring  down  the  fusion 
point  to  the  capacity  of  an  ordinary  furnace.  The  properties 
of  the  alloy  will  be  described  hereafter. 

The  two  metals  are  easily  separated  from  one  another  by  the 
following  process.  The  alloy  is  dissolved  in  aqua  regia,  and 
sal  ammoniac  added  to  the  solution,  which  is  evaporated  on  a 
water-bath  nearly  to  dryness.     Care  is  necessary  that  the  heat 

•  The  absurdly  high  prices,  charged  by  furnishing-houses  for  chemical 
apparatus  made  from  this  metal,  are  no  index  of  its  actual  commercial 
value,  but  only  of  the  necessities  and  easy  temper  of  chemists. 


PLATINUM.  423 

be  not  too  great,  and  for  this  reason  the  water-bath  is  used. 
Should  the  temperature  be  raised  too  high,  part  of  the  chloride 
of  gold  would  be  dissolved,  and  the  parting  of  the  metals  be  im- 
possible, without  a  new  solution.  The  concentration  having  been 
carried  so  far  that  the  yellow  precipitate  of  platino-chloride  of 
ammonia  is  just  moistened  by  the  remaining  solution,  alcohol  is 
added,  and  the  double  chloride  washed  till  the  liquid  comes  off 
no  longer  colored.  In  this  manner  all  the  gold  is  dissolved,  and 
the  platinum  remains  behind,  in  combination  with  chlorine  and 
ammonium.  This  double  salt  is  ignited  to  obtain  spongy  plati- 
num, and  the  alcoholic  solution  precipitated  with  protosulphate 
of  iron,  or  oxalic  acid,  if  no  foreign  metal  be  present,  yields 
metallic  gold. 

Another  mode,  less  expeditious  than  the  former,  is  to  fuse  the 
alloy  with  silver,  mill  it  out  into  thin  foil,  roll  it  up,  and  treat 
it  with  nitric  acid,  which  dissolves  the  silver  and  platinum. 
These  are  to  be  separated  as  hereafter  described. 

Silver  and  Platinum. — We  have  already  said  that  the  alloy 
of  these  two  metals  is  soluble  in  nitric  acid,  to  which  it  commu- 
nicates a  straw  yellow  tint.  From  this  solution  the  silver  is 
easily  precipitated  by  means  of  hydrochloric  acid.  The  alloy 
may  be  directly  acted  on  by  sulphuric  acid  in  the  same  manner 
already  described  under  the  head  of  gold.  Silver  dissolves  in 
the  acid,  and  platinum  is  left  behind. 

Copper  and  Platinum. — This  alloy  is  most  conveniently  ana- 
lyzed by  dissolving  it  in  aqua  regia,  evaporating  to  expel  nitric 
acid,  and  precipitating  platinum  by  means  of  metallic  copper. 
Or,  the  copper  may  be  dissolved  out  with  nitric  or  sulphuric 
acid,  in  which  the  platinum  of  this  combination  is  insoluble. 
The  latter  plan  will  not  succeed  when  the  platinum  is  in  suflS- 
cient  quantity  to  protect  the  copper,  or  when  gold  is  present  in 
large  proportion. 

Copper,  Gfold,  Silver,  and  Platinum. — An  alloy  of  this  kind 
may  be  cupelled  to  get  rid  of  the  copper,  and  the  other  metals 
separated,  as  already  described,  or  it  may  be  dissolved  in  boiling 
aqua  regia,  which  leaves  the  silver  behind  as  a  chloride  and 
takes  up  the  remaining  metals.  The  farther  process  resembles 
the  separation  of  gold  from  platinum  already  described.    Chloride 


424      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  copper  is  soluble  in  alcohol  as  well  as  chloride  of  gold,  and,  as 
before,  the  platino-chloride  of  ammonium  is  left  behind.  The  gold 
and  copper  are  easily  separated  by  protosulphate  of  iron.  The 
choice  of  these  methods  will  be  regulated  by  the  relative  pro- 
portions of  the  metals  in  the  alloy.  If  the  copper  is  in  very 
small  quantity  compared  with  the  gold,  silver,  and  platinum, 
cupellation  will  be  advisable ;  if  not,  the  latter  plan  should  be 
adopted. 

PLATINUM   AND   ITS   NON-SALINE   COMPOUNDS. 

Platinum. — When  pure,  it  is  a  soft,  flexible  metal,  resembling 
silver  in  color,  but  inferior  to  it  in  brilliancy.  It  is  very  mal- 
leable, and  may  be  hammered  into  leaves  so  thin  as  to  be  blown 
away  by  the  breath.  It  may  be  drawn  into  wires  the  two- 
thousandth  of  an  inch  in  diameter,  and  by  coating  it  with  silver, 
drawing  it  out,  and  dissolving  off  the  investing  metal,  it  may  be 
reduced  to  a  very  much  finer  wire.  A  small  quantity  of  iridium 
greatly  diminishes  its  softness,  malleability,  and  ductility  ;  hence 
the  necessity  of  separating  this  metal  perfectly. 

It  is  entirely  unchangeable  in  either  moist  or  dry  air  ;  it  is  not 
fused,  tarnished,  nor  in  any  way  altered  by  the  highest  heat  of  a 
smith's  forge.  The  oxyhydrogen  blowpipe  and  galvanism  can 
alone  break  up  the  powerful  cohesion  of  its  particles.  Dr.  Hare 
succeeded  in  fusing  so  large  a  quantity  as  28  ounces  of  it  at  once 
by  means  of  his  powerful  oxyhydrogen  blowpipe.  This  immu- 
tability of  platinum  at  ordinary  temperatures  renders  it  an  in- 
valuable substance  to  the  analytical  chemist,  who  employs  it  for 
capsules,  crucibles,  wires  for  blowpipe  manipulations,  &c.  It 
requires,  however,  caution  in  its  use,  for  it  is  quite  possible  to 
destroy  the  utensils  made  of  it,  as  has  already  been  said  in  the 
preliminary  chapter  on  metallurgic  operations. 

This  metal  was  used  at  one  time  by  the  Russian  government 
for  the  manufacture  of  coins.  The  coinage  consisted  of  several 
pieces,  the  largest  of  which  was  the  twelve-rouble  piece  contain- 
ing 638  grains  of  pure  Ural  platinum.  Now,  a  rouble  is  worth  75 
cents,  and  its  equivalents  in  the  different  precious  metals  are 
18.5  grains  of  pure  gold,  53.16  grains  o?  coined  platinum,  and 
277.4  grains  of  pure  silver.     Platinum,  therefore,  after  being 


PLATINUM.  •  425 

worked  up,  is  worth  a  little  more  than  |-  as  much  gold.  The 
relative  value  of  these  three  metals,  at  that  time  in  Russia,  will 
be  better  seen  bj  a  reduction  of  these  to  ounce  values.  An 
ounce  of  gold  was  worth  $19.20  ;  an  ounce  of  platinum,  after 
coinage,  $7.02,  and  an  ounce  of  pure  silver,  $1.30.  The  rapid 
deterioration  of  the  metal  in  value,  in  consequence  of  the  in- 
creased amount  coined  and  thrown  into  the  market,  compelled 
the  recall  of  this  coinage. 

Platinum  sponge  is  irregular,  loose,  and  porous  in  its  struc- 
ture, as  its  name  imports.  It  is  made  by  igniting  the  double 
chloride  of  platinum  and  ammonium,  till  all  the  volatile  alkalies 
and  the  chlorine  are  driven  off.  Its  density  depends  upon  the 
amount  of  heat  used  to  expel  the  volatile  portions  of  the  double 
salt.  The  higher  this  is,  the  more  dense  is  the  resulting 
sponge,  so  that  when  a  very  loose,  open  sponge  is  required,  the 
heat  must  be  the  lowest  possible  ignition. 

Platinum  black  is  the  most  minutely  divided  form  in  which 
this  metal  is  obtained.  It  is  made  by  fusing  platinum  with  cop- 
per, zinc,  or  potassium,  and  dissolving  out  copper  with  nitric 
acid,  zinc  with  nitric  and  then  with  sulphuric  acid,  and  potas- 
sium with  water.  Or  a  mixed  solution  of  platinum  and  iron  may 
be  precipitated  with  ammonia,  and  ignited  in  an  atmosphere  of 
hydrogen.  The  iron  being  then  dissolved  out  by  hydrochloric 
acid,  the  platinum  is  left  behind  in  fine  powder ;  or,  finally,  this 
preparation  may  be  obtained  by  throwing  down  the  metal  from 
its  solutions  by  means  of  zinc  or  organic  substances.  Liebig's 
method  is  to  dissolve  chloride  of  platinum  in  a  hot,  concentrated 
solution  of  potassa,  and  immediately  to  pour  alcohol  upon  it, 
constantly  stirring  the  mixture  till  effervescence,  showing  the 
escape  of  carbonic  acid,  takes  place.  The  supernatant  fluid  is 
poured  off  from  the  precipitate,  which  is  thoroughly  washed  by 
boiling  it  first  with  alcohol,  then  with  hydrochloric  acid,  then 
with  potassa,  and  finally  repeatedly  with  water.  It  is  dried  by 
evaporation. 

These  two  preparations  of  platinum  are  possessed  of  very 
remarkable  and  energetic  powers.  They  condense  gases  with 
great  force,  and  sometimes  with  such  rapidity  as  to  drive  out 
sufficient  latent  heat  to  ignite  the  metal.     This  property  was 


426      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

first  discovered  in  the  sponge,  by  Professor  Doebereiner,  of  Jena, 
in  1824.  He  found  that  a  jet  of  hydrogen  gas  directed  upon 
spongy  platinum  in  the  open  air,  gradually  heated  it  so  intensely 
that  the  metal  became  red,  and  set  fire  to  the  gas.  A  number 
of  scientific  toys  were  constructed  to  exhibit  this  experiment, 
and  an  attempt  was  made  to  make  it  subserve  the  purpose  of 
speedy  illumination,  now  so  much  more  conveniently  and  cheaply 
accomplished  by  friction  matches.  Doebereiner  says  that  the 
sponge  absorbs  oxygen,  but  not  nitrogen,  from  the  air.  Liebig's 
black  is  said  to  absorb  250  times  its  volume  from  the  atmosphere. 
If  this  be  true,  it  shows  a  wonderful  faculty  of  condensation, 
for,  estimating  the  pores  of  the  black  at  one-fourth  its  entire 
volume,  a  calculation  which  can  hardly  be  considered  too  low, 
the  tension  of  the  included  air  and  its  consequent  condensation 
would  be  equal  to  a  thousand  atmospheres.  It  unites  gases, 
forming  water  when  placed  in  an  atmosphere  of  mingled  oxygen 
and  hydrogen.  Platinum  wire,  heated  to  122°,  will  do  the  same 
thing.  It  also  combines  sulphurous  acid  and  oxygen,  forming 
sulphuric  acid.  It  oxidates  alcohol,  producing  acetic  acid,  and, 
if  the  action  be  sufficientl}''  protracted,  converts  this  into  car- 
bonic acid  and  water.  Nor  is  this  force  confined  to  gases. 
Introduced  into  a  solution  of  potassa  and  its  nitrate  in  alcohol, 
it  produces  carbonic  acid  and  ammonia.  To  produce  these 
effects,  it  is  necessary  that  the  platinum  used  should  have  the 
purest  possible  surface,  that  is  to  say,  it  should  have  nothing  on 
it  but  pure  water.  To  attain  this,  potassa  should  be  fused  on 
the  surface  of  the  sponge,  which  must  then  be  washed  in  pure 
water,  dipped  in  oil  of  vitriol,  and  again  thoroughly  cleansed 
with  water.  The  black  may  be  cleansed  by  boiling  it  in  sul- 
phuric acid  and  washing  with  water  and  solution  of  ammonia. 

Platinum  is  the  heaviest  of  the  metals.  The  specific  gravity 
of  the  forged  metal  is  21.25;  that  of  the  wire  21.5.  Its  equiva- 
lent, according  to  Berzelius,  is  98.68  on  the  hydrogen,  and 
1233.499  on  the  oxygen  scale.     Its  symbol  is  Pt. 

Oxide  of  Platinum,  PtCl.  106.68. — Protoxide  of  platinum 
is  obtained  by  digesting  the  protochloride  in  potassa  water, 
excess  of  this  agent  being  avoided,  since  it  dissolves  a  portion 
of  the  oxide,  forming  a  green  solution.     It  is  a  black  hydrate, 


PLATINUM.  427 

■which  loses  its  water  hj  a  gentle  heat,  and  its  oxygen  by  igni- 
tion. It  dissolves  slowly  in  acids,  forming  salts  which  are  brown, 
green,  red,  or  colorless. 

It  is  precipitated  as  a  brown  sulphiiret,  by  sulphuretted 
hydrogen,  and  the  precipitate  is  redissolved  by  hydrosulphuret 
of  ammonium.  It  forms  with  ammonia,  by  precipitation  of  its 
sulphuric  acid  solution,  a  compound  which  has  been  Avritten 
NH3,Pt04-NH^O.  When  kept  for  some  time  at  a  temperature 
of  212°  F.,  it  loses  water  and  ammonia,  and  becomes  NH3Pt,0, 
or  NlljiPtO,  which  is  insoluble  in  water  or  ammonia,  and  forms 
explosive  salts. 

Binoxide  of  Platinum^  ^^^2-  114.68, — This  oxide  is  pre- 
cipitated as  a  hydrate  from  its  solutions.  Berzelius  recommends 
that  the  sulphate  of  platinum  should  be  exactly  decomposed  by 
nitrate  of  baryta.  Sulphate  of  baryta  falls,  and  nitrate  of  pla- 
tinum remains  in  solution.  The  liquid  is  filtered,  and  the  filtrate 
treated  with  pure  soda  till  about  half  the  oxide  is  thrown  down. 
Should  the  precipitation  be  carried  too  fiir,  a  basic  salt  will  fall. 
It  comes  down  as  a  yellowish-brown  hydrate,  and,  when  dry, 
resembles  iron  rust.  Water  can  be  expelled  at  a  moderate  heat, 
but  a  little  increase  of  temperature  drives  off  oxygen,  reducing 
it  to  the  protoxide,  and,  if  pushed  far  enough,  to  metal. 

Its  salts  are  formed  indirectly  from  the  bichloride  and  alka- 
line salts.  They  are  yellow  or  brown,  and  readily  let  fall 
metallic  platinum  when  acted  on  by  organic  substances. 

Protosidpliuret  of  Ju»?a^mw??i  (PtS)  is  a  blue-black  powder, 
which  loses  sulphur  by  simple  ignition  in  the  air.  It  may  be 
obtained  by  precipitating  a  protosalt  by  means  of  an  alkaline 
sulphuret,  or  by  heating  the  sponge  or  black  in  a  covered 
crucible  with  sulphur. 

BisuJpliuret  of  platinum  (PtSj)  is  a  blackish-gray  powder, 
which  decomposes  like  the  last  described  sulphuret.  It  is  made  by 
precipitating  the  persalts  with  alkaline  sulphurets,  or  by  heating 
a  mixture  of  3  parts  of  the  yellow  double  chloride  of  ammonium 
and  platinum  with  2  parts  of  sulphur. 

Phosphuret  of  platinum  is  white,  metallic,  brittle,  and  fusible. 
It  is  formed  whenever  phosphorus  and  platinum  are  heated 
together. 


428      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

Nitruret  of  Platinum. — The  compound  of  protoxide  of  plati- 
num and  ammonia  already  described,  ■when  kept  in  a  retort  at 
356°,  gradually  parts  with  all  its  hydrogen  and  oxygen,  which 
pass  off  in  the  form  of  aqueous  vapor,  and  a  compound  of  three 
equivalents  of  platinum  with  one  of  nitrogen  (PtjN)  remains. 
When  heated  to  374°,  nitrogen  suddenly  flies  off,  and  metallic 
platinum  remains. 

ALLOYS. 

Platinum  readily  unites  with  other  metals  when  heated  with 
them.  The  union  is  sometimes  so  rapid  that  it  is  attended  with 
the  evolution  of  heat  and  light.     The  alloys  are  fusible. 

Potassium  and  sodium  form  with  it  alloys  which  are  shining, 
brittle,  and  decomposable  by  water.  Antimony  makes  a  steel 
gray,  brittle,  crystalline  alloy ;  and  arsenic,  a  brittle  and  very 
fusible  compound.  Both  these  may  be  decomposed  by  heating 
them  in  the  air ;  the  oxidizable  metal  being  driven  off,  the  other 
remaining.  The  alloy  with  arsenic  melts  at  a  little  above  red- 
ness, and  can  be  cast  in  moulds. 

With  bismuth  and  with  zinc,  its  alloys  are  bluish-white,  brit- 
tle, and  fusible  ;  with  lead,  reddish  and  brittle.  Tin  forms  a 
silver  white  alloy  with  it,  and  so  greatly  increases  its  fusibility 
that  it  is  hazardous  to  solder  a  platinum  vessel  with  tin  solder. 
Gold  is  commonly  used  as  a  solder  for  platinum.  With  iron,  its 
alloy  is  hard  and  malleable,  and  not  readily  acted  on  by  acids. 
One  part  of  platinum  forms  with  ninety-nine  of  iron,  a  compound 
which  is  not  attacked  by  nitric  acid.  To  steel  it  communicates 
toughness,  and,  in  certain  quantities,  protects  it  from  tarnish. 
With  copper  it  forms  a  pale  yellow,  or  yellowish-gray  malleablej 
alloy,  which  has  been  used  in  Paris  for  dental  purposes.  Vonj 
Eckart's  alloy  is  highly  elastic,  a  property  which  it  does  not] 
lose  by  annealing.  It  is  of  the  same  specific  gravity  as  silver, 
and  not  subject  to  tarnish.  It  may  be  hammered,  rolled,! 
polished,  and  drawn  to  the  finest  wire.  It  is  composed  of  plati- 
num, 2.40  ;  silver,  3.53  ;  copper,  11.71. 

The  alloy  with  silver  is  hard,  and  not  subject  to  tarnish  by! 
Bulphur. 


PLATINUM.  429 

The  alloy  ■with  gold  is  of  a  straw  yellow  color,  approaching 
white,  and  has  a  crystalline  surface.  It  is  less  fusible  than 
gold.  Its  behavior  upon  the  cupel  and  with  nitric  acid  has 
already  been  described  in  the  chapter  on  gold.  Its  alloys  with 
palladium  and  iridium  are  native,  and  have  the  same  general 
appearances  Avith  the  metal  itself.  The  method  of  separating 
the  different  constituent  parts  of  these  compounds  has  already 
been  described. 

HALOID    SALTS. 

ProtocJiloride  of  Platinum,  PtCl. — When  the  deutochloride 
of  platinum  is  heated  to  the  melting  point  of  tin,  one  equivalent 
of  chlorine  is  given  off,  and  this  substance  remains. 

It  is  a  greenish-gray  powder,  insoluble  in  water  or  the  ox- 
acids, but  partially  soluble  in  hydrochloric  acid.  Aqua  regia 
forms  with  it  the  red  bichloride  of  platinum.  The  chlorides 
of  potassium,  sodium,  and  ammonium,  combine  with  it  to  red, 
double  salts,  which  have  the  form  of  KCl,PtCl.  At  a  red  heat 
it  parts  with  all  its  chlorine. 

Ammoniacal  Protoclilorides  of  Platinum. — The  combinations 
of  ammonia  with  chloride  of  platinum  are  so  interesting,  and 
have  been  used  by  Liebig  so  effectively  for  illustrating  the  laws 
of  combination  of  certain  compound  radicals,  that  a  somewhat 
minute  description  of  them  here  can  scarcely  be  considered 
foreign  to  the  general  purpose  of  this  work. 

G-reen  Substance  of  Magnus. — This  ammoniacal  protochloride 
of  platinum  was  first  discovered  by  Magnus,  and  hence  has  re- 
ceived from  Liebig  the  name  which  we  give.  It  is  made  by 
digesting  the  protochloride  of  platinum  in  hot  water  of  ammo- 
nia, which  speedily  converts  it  into  a  dark,  grass  green,  inso- 
luble, crystalline  substance.  Or  the  same  substance  may  be 
formed  by  dissolving  protochloride  of  platinum  in  boiling,  mode- 
rately dilute  hydrochloric  acid,  and  pouring  the  solution  into 
hot  water  of  ammonia,  or  carbonate  of  ammonia,  when  green 
shining  scales  of  pure  ammoniacal  protochloride  of  platinum 
subsides.  Or  sulphurous  acid  may  be  added  to  the  bichloride 
of  platinum,  till  it  no  longer  throws  down  a  yellow  precipitate 


430   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

from  solution  of  sal  ammoniac  ;  and  then  excess  of  hot  water  of 
ammonia  being  added,  the  mixture,  as  it  cools,  lets  fall  the  same 
green  crystals.  The  principle  in  all  these  modifications  of  the 
process  is  the  same.  In  all  of  them,  protochloride  of  platinum 
is  brought  in  contact  with  ammonia  at  a  high  temperature,  and 
a  combination  ensues  between  the  two  bases. 

The  formula  of  this  double  salt  is  PtCl,NH3.  Boiled  with 
water  for  some  time,  an  isomeric  yellow  salt  is  obtained. 

Yelloiv  Salt  of  Reiset.  Meiset's  Ohlorammonium-platinamid. — 
Reiset  discovered  that,  when  the  green  substance  just  described 
is  digested  for  some  time  in  hot  caustic  ammonia,  a  yellow  solu- 
tion is  obtained,  which,  upon  evaporation,  yields  a  great  quan- 
tity of  yellowish-white,  long,  prismatic,  shining  crystals.  These 
dissolve  in  water,  and  the  substance  may  be  precipitated  from 
the  aqueous  solution  by  the  addition  of  alcohol.  The  same  salt 
may  be  obtained  from  the  boiling  hydrochloric  solution  of  proto- 
chloride of  platinum,  by  gradually  adding  to  it  carbonate  of  am- 
monia till  it  becomes  yellow.  A  green  substance  subsides,  and  the 
solution  is  filtered.  As  it  cools,  the  yellow  NH3,PtCl2  separates, 
and  alcohol  precipitates  Reiset's  salt  from  the  clear  liquid 
above. 

The  formula  of  this  salt  in  crystals  is  PtCl,2NH3  + Aq,  or 
PtNH,+  NH,Cl  +  Aq. 

The  behavior  of  these  compounds  is  very  remarkable.  They 
have  no  alkaline  reaction.  Ammonia  is  not  eliminated  from 
them  by  either  potassa  or  lime.  Upon  the  green  insoluble  salt, 
hydrochloric  and  dilute  sulphuric  acids  have  no  efi'ect.  Nitric 
acid  dissolves  it  with  rapid  evolution  of  nitrous  fumes,  and  nume- 
rous white  scales  crystallize  out  of  the  solution  as  it  cools,  while 
not  a  trace  of  ammonia  can  be  detected  in  the  mother  liquor. 
A  new  base  has  now  been  formed  by  the  separation  of  half  the 
platinum  and  chlorine  from  the  salt  of  Magnus  and  the  acces- 
sion of  an  atom  of  oxygen.  This  will  be  made  clearer  by  a 
juxtaposition  of  the  formulae  of  the  two  salts  : — 

The  green  substance  of  Magnus  is        .         .      Pt2Cl2N2Hg. 
The  new  base,  which  combines  with  the  nitric 

acid  is PtClN,H,0. 


I 


\ 


PLATINUM.  431 

Salts  may  be  formed  from  this  new  base  in  the  same  manner 
as  from  a  simple  metallic  oxide,  the  different  acids  being  sub- 
stituted for  nitric  acid. 

Thus  the  nitrate  is   ....      PtClN2HgO  +  N03. 
The  sulphate  is         ....      PtClN2HgO  +  S03. 

If  a  solution  of  the  nitrate  be  mixed  with  hydrochloric  acid, 
a  heavy  crystalline  powder  is  obtained,  the  chloride  of  the  com- 
pound radical. 

The  formula  of  the  compound  radical  itself,  then,  is  PtClN2Hg. 
The  oxide,  which  forms  salts  with  sulphuric,  nitric, 

and  other  acids,  is  ....         PtClNjHgO. 

The  chloride,  obtained  as  just  described  .         PtClNjHgCl. 

Gros,  who  discovered  these  salts,  did  not  isolate  the  base, 
though  its  existence  is  most  conclusively  proved. 

Reiset's  salt  is  equally  remarkable,  for  it  behaves  precisely 
like  the  chloride  of  a  metal.  A  comparison  of  its  behavior 
with  that  of  sal  ammoniac  shows  this  most  conclusively.  It  will 
be  remembered  that  when  the  last-named  salt  is  treated  with 
sulphuric  acid,  its  chlorine  is  driven  off,  and  a  sulphate  of  the 
oxide  of  ammonium  remains.  Farthermore,  when  a  solution  of 
sal  ammoniac  is  mixed  with  a  solution  of  bichloride  of  platinum, 
a  double  salt  is  formed. 

Now,  in  both  these  cases,  Reiset's  compound  behaves  pre- 
cisely like  sal  ammoniac.  It  is  PtN2Hg,Cl,  and  the  PtNgHg  is 
the  radical  which  corresponds  to  the  NH^  of  the  sal  ammoniac. 
Sulphuric  acid  drives  off  chlorine  and  forms  a  sulphate  of  the 
oxide  of  the  radical.  Perchloride  of  platinum  forms  a  double 
salt  with  the  compound  corresponding  to  the  double  chloride  of 
platinum  and  ammonium,  and  another  containing  only  half  the 
quantity  of  bichloride  of  platinum. 

The  oxide  of  this  base  may  be  separated  from  its  combina- 
tions. If  to  the  sulphate  baryta  be  carefully  added,  so  as  ex- 
actly to  precipitate  the  sulphuric  acid  as  sulphate  of  baryta,  the 
pure  basis  is  retained  in  solution  and  may  be  obtained  in  trans- 
parent colorless  needles,  by  evaporation  in  the  receiver  of  an 
air-pump.      This  basis  contains  the  elements  of  protochloride 


432      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  platinum,  ammonia,  and  water  (PtCl,2NH34-HO).  It  resem- 
bles in  its  behavior  a  caustic  fixed  alkali,  destroying  the  skin, 
expelling  ammonia  from  its  salts,  and  precipitating  the  metallic 
, oxides  from  their  solutions.  From  a  mixture  of  grape  sugar  and 
sulphate  of  copper,  it  throws  down  peroxide  of  copper  and  redis- 
solves  it  when  added  in  excess.  When  this  mixture  is  heated, 
the  peroxide  is  reduced  to  protoxide,  in  the  same  manner  as 
when  caustic  potash  is  present. 

Heated  to  100°,  this  basis  is  decomposed,  ammonia  and  water 
escape,  and  there  remains  a  substance  (PtOjNHj)  which  com- 
bines with  acids  to  form  salts,  and  which  burns  in  the  air  with 
evolution  of  ammonia,  leaving  metallic  platinum.  ■ 

When  the  platinum  basis  is  brought  in  contact  with  hydro- 
chloric acid,  water  is  formed,  and  the  substance  originally  ob- 
tained by  solution  of  the  pure  protochloride  of  platinum  in 
ammonia  is  reproduced.  When  the  dry  chlorine  compound  is 
heated  to  130°  or  150°,  ammonia  escapes,  and  the  yellow  isome- 
ric modification  of  the  salt  of  Magnus  remains. 

When  treated  with  nitrate  of  silver,  the  yellow  salt  decom- 
poses. Chloride  of  silver  and  two  new  salts,  containing  nitric 
acid  and  platinum,  result,  one  of  them  crystallizing  in  yellow 
transparent  octahedra.  l 

If  the  sulphate  of  the  oxidized  platinum  basis  (PtNgHgOjSOj)  * 
be  mixed  with  iodide  of  barium,  the  double  decomposition  pro- 
duces sulphate  of  baryta,  and  an  iodine  compound  (PtNgHgl), 
corresponding  to  the  protoxide.  This  protoxide  is  soluble  in 
water,  and  decomposes  on  boiling  into  ammonia,  and  an  iodine 
compound  analogous  to  the  salt  of  Magnus  (PtNH3,I). 

When  this  iodide  is  treated  with  nitrate  or  sulphate  of  silver, 
iodide  of  silver  is  formed,  together  with  the  nitrate  or  sulphate 
of  a  new  base,  containing  one  equivalent  of  ammonia  less 
(PtNH304-N03)  (PtNH30,S03). 

Treated  with  hydrochloric  acid,  these  salts  form  the  yellow 
ammoniacal  protochloride  of  platinum  ;  and  when  digested  in 
water  of  ammonia,  they  are  transformed  into  the  nitrate  or  sul- 
phate of  the  first  series. 

"  According  to  the  different  notions  entertained  respecting  the 
constitution  of  the  salts,  the  new  platinum  bases  may  be  con- 


PLATINUM.  433 

sidered  as  true  alkalies,  i.  e.  as  the  oxides  of  a  compound  radical 
formed  by  platinum  and  the  elements  of  ammonia,  and  performing 
the  part  of  a  metal.  Assuming  this  to  be  the  correct  view,  we 
should  have,  in  the  first  series,  as  the  formula  of 


The  radical  ....         PtN,H,. 

2        0 

The  oxide   . 
The  chloride 
The  nitrate 
The  sulphate 


PtN,H,0. 
PtN,H,Cl. 
PtN^H.O+NO,. 
PtN,H,0  +  S03. 


Or,  if  we  assume  the  constitution  of  these  salts  to  be  analogous 
to  that  of  the  ammoniacal  salts,  the  radical  would  correspond  to 
ammonium  ;  the  hydrogen  compound,  therefore,  would  be,  in  its 
chemical  character,  analogous  to  ammonia  ;  the  chlorine  com- 
pound would  contain  the  elements  of  hydrochloric  acid ;  the 
nitrate  or  sulphate  would  contain  the  elements  of  the  hydrated 
nitric  or  sulphuric  acid. 

"According  to  this  view,  the  formula  of  the  compound  corre- 
sponding 

To  ammonia  would  be  .         .  PtNjHj. 

Of  that  corresponding  to  ammonium  PtNjH^-f-H. 

Of  the  oxide         ....  PtN^H.+  HO. 

Of  the  nitrate      ....  PtN^H^+HO,^"©,. 

Of  the  sulphate    ....  PtN2H,+  HO,S03. 

"  According  to  this,  the  basis  of  the  salts  of  Gros  would  differ 
from  the  basis  of  the  last  two  salts,  only  inasmuch  as  it  contains 
one  equivalent  of  chlorine  ;  and,  indeed,  the  nitrate  of  the  non- 
chloruretted  basis  of  Reiset  seems,  upon  the  addition  of  a  solution 
of  chlorine,  to  become  directly  transformed  into  the  nitrate  of 
the  chloruretted  basis  of  Gros  ;  at  least  a  nitrate  is  obtained, 
by  this  operation,  possessing  the  properties  of  the  latter ;  the  addi- 
tion of  solution  of  iodine  gives  rise  to  the  formation  of  a  nitrate 
corresponding  apparently  to  the  nitrate  of  the  ioduretted  bases. 

"That  which  is  most  worthy  of  attention  in  these  combinations, 

is  the  circumstance  that  in  these  three  bases  which  have  been 

formed  by  the  accession  of  platinum  to  the  elements  of  ammonia, 

we  do  not  observe  the  slightest  alteration  in  the  chemical  character 

28 


434   CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

of  this  latter  substance.  This  fact  leads  us  to  the  inference  that 
the  addition  of  the  extraneous  body,  i.  e.  its  accession  to  the 
elements  of  the  ammonia,  has  not  caused  any  alteration  in  the 
constitution  of  the  latter  body.  And  here  we  need  only  to 
recall  to  our  minds  the  constitution  of  the  acids  and  their  de- 
portment. Acids  are  hydrogen  compounds  of  simple  or  of 
compound  radicals,  the  chemical  character  of  which,  as  acids, 
depends  upon  their  amount  of  hydrogen  replaceable  by  metals ; 
their  principal  characteristic  properties  are  independent  of  the 
number  of  elementary  atoms  contained  in  the  atom  of  the  radi- 
cal ;  we  see  these  elementary  atoms  increase  or  decrease  in 
number  without  their  increase  or  decrease  exercising  any  influ- 
ence upon  the  properties  of  the  acid  as  an  acid. 

"Now  we  have  admitted  ammonia  to  be  the  hydrogen  compound 
(hydruret)  of  amidogen ;  that  is,  of  a  radical,  the  chemical  cha- 
racter of  which  is  evidently  and  decidedly  the  very  opposite  to 
that  of  the  radical  of  an  acid ;  and  we  may  assume  that,  by  the 
accession  of  a  compound  substance,  or  of  a  new  radical  to  the 
atom  of  ammonia,  there  ensues  the  formation  of  the  hydrogen 
compound  (hydruret)  of  a  compound  amide,  retaining  the  pro- 
perties of  the  ammonia,  and  this  precisely  because  the  ehemical 
constitution  upon  which  the  chemical  j^rojjerties  depend  has  re- 
mained unaltered.  Of  course  this  can  only  take  place  in  cases 
where  the  chemical  properties  of  the  substance  added  are  either 
analogous  or  similar  to  the  chemical  properties  of  the  radical  to 
which  the  substance  is  added,  and  with  which  it  combines  ;  for,  - 
if  these  properties  were  dissimilar  or  opposite,  the  chemical  ^ 
character  of  the  radical  would,  of  necessity,  suffer  some  alter- 
ation ;  nay,  under  some  circumstances,  it  might  be  altogether 
annihilated  by  the  addition  of  a  compound  of  opposite  properties 
to  those  of  the  radical. 

"  Ammonia  is  the  hydruret  of  amidogen ;  by  the  accession  of 
the  amide  of  the  protochloride  of  platinum,  or  by  that  of  the 
^mide  of  platinum,  the  hydruret  of  a  compound  amide  is  formed. 

Ammonia  ....         Ad-j-H~\  C      Radical 

Added  to  this  '  =  PtClAd2+H  -|        of  the 

Amide  of  protochloride  of  platinum  PtClAd  \  {^basis  of  Gros. 


PLATINUM.  435 

Or 

Ammonia  ....         Ad-f-H  \  C      Radical 

Added  to  this  (■  =  PtAd24-H    I         of  the 

Amide  of  platiniim  .  .  PtAd     \  IbasisofReiset. 

The  basis  of  lleiset  is  PtN2H60,  or  PtNjH.+HO. 
The  chlorine  compound  is  PtN2H5Cl,  or  PtN2H5+HCl. 

"  In  this  chlorine  compound  we  may  assume  chlorine  to  exist 
as  an  ultimate  constituent  in  the  form  of  hydrochloric  acid.  It 
is  farther  possible  that,  as  Reiset  is  inclined  to  think,  the  acces- 
sion of  a  metallic  oxide — of  protoxide  of  platinum,  for  instance — 
to  the  elements  of  ammonia,  imparts  to  the  latter  the  properties 
of  a  base,  just  in  the  same  manner  as  the  accession  of  protoxide 
of  hydrogen  (water)  does.  In  this  case,  the  metal  of  the  metal- 
lic oxide  would  perform  exactly  the  same  part  as  the  hydrogen 
does. 

^    .    .  .      ,      1      I  NF,  )  f  NH,  I  Basis  in  the  platinum  salts 

Basis  m  the  ammoniacal  salts  i   u^     r  —  i   t>, ^    1^^0.1  1       • 

(  HO    )        (  PtO  )       of  the  second  series. 

Basis  in  cuprum  sulphurico-     |  2NH3  ]        J  2NH3  1     Platinum  basis  of  the 

ammoniatum  i  HO     j        \  PtO    j  salts  of  Keiset. 

"  Upon  looking  at  the  chlorine  compound  of  the  basis  of  Gros, 
we  farther  find  that  this  compound  contains  the  elements  of 
perchloride  of  platinum  and  of  ammonia  : — 

Chlorine  compound  of  Gros,  PtClN^HgCl,  or  PtClN^H^+Cl. 
Ammoniated  perchloride  of  platinum,  PtCl2  +  N2Hg. 

"  Now  we  find,  in  fact,  that  perchloride  of  platinum,  when 
thrown  into  a  warm  solution  of  ammonia,  dissolves .  therein  to  a 
large  amount,  forming  a  nearly  colorless  fluid,  which,  upon  the 
addition  of  alcohol,  yields  a  copious,  white,  flocculent  precipi- 
tate. By  treating  this  precipitate  with  nitric  acid,  a  crystal- 
lizable  and  soluble  white  salt  is  obtained,  very  similar  to,  or — 
what  is  highly  probable — identical  with  the  nitrate  of  the  basis 
of  Gros.  The  precipitate  itself,  however,  shows  by  no  means 
the  properties  of  the  chlorine  compound  of  the  basis  of  Gros ; 
for  this  latter  is  yellow,  and  of  very  difficult  solubility  in  water, 
whilst  the  ammoniacal  perchloride  of  platinum  is  partially  rede- 
composed  upon  evaporation,  and  of  exceedingly  easy  solubility 
in  water."* 

*  Liebig,  Lectures  on  Organic  Chemistry. 


436     CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

If  it  be  thought  that  too  much  space  has  been  expended  upon 
the  history  of  these  remarkable  reactions,  the  author's  only 
apology  must  be  made  in  the  words  of  the  great  chemist  from 
whom  he  has  so  largely  quoted :  "  I  have  entered  upon  this 
discussion  of  the  properties  and  deportment  of  these  remarkable 
bases  principally  because  it  will  tend  to  elucidate  the  nature  of 
a  great  and  important  class  of  compounds,  which,  as  true  or- 
ganic bases,  do  not  comport  themselves  like  the  metallic  oxides, 
but  like  ammonia ;  the  saturating  capacity  of  which  does  not 
depend,  as  is  the  case  with  the  metallic  oxides,  upon  their 
amount  of  oxygen,  but  upon  a  certain  and  definite  amount  of 
hydrogen  in  the  acid  which  is  added  to  their  elements." 

Bicldoride  of  Platmum,  PtClj. — This  chloride  is  obtained  by 
dissolving  platinum  in  nitro-hydrochloric  acid,  and  evaporating 
to  dryness  at  a  very  gentle  heat,  when  it  remains  as  a  red  hy- 
drate, becoming  brown  after  the  expulsion  of  its  water.  Should 
the  heat  be  too  high,  the  salt  is  partially  decomposed,  protochlo- 
ride  of  platinum  being  formed,  which  gives  it  a  darker  color. 
The  best  mode  of  regulating  the  heat  is  to  use  a  water-bath.  It 
crystallizes  with  ten  equivalents  of  water. 

When  free  from  palladium  and  iridium,  and  from  protochlo- 
ride  of  platinum,  its  solution  is  yellow,  with  a  reddish  cast.  It 
is  very  soluble  and  highly  deliquescent.  Its  ethereal  solution 
gradually  deposits  metallic  platinum.  Heat  reduces  it  first  to 
protochloride  and  then  to  metal. 

The  bichloride  of  platinum  forms  double  salts  with  many 
metallic  chlorides.  The  double  chloride  of  sodium  and  plati- 
num, NaCljPtClj+GHO,  is  crystallizable  and  soluble  both  in 
water  and  alcohol.  The  potassium  salt  (KCljPtClj)  is  lemon 
yellow,  scarcely  soluble  in  cold  water,  a  little  more  soluble  in 
hot  water,  insoluble  in  alcohol  of  60  per  cent.  At  a  full  red 
heat  it  is  decomposed,  chlorine  being  driven  off,  and  metallic 
platinum  and  chloride  of  potassium  being  left  behind.  The 
ammonium  salt  (NH^CljPtCla)  has  the  same  degree  of  solubility 
as  the  potassium  salt,  but  it  is  more  easily  decomposed  by  heat, 
leaving  nothing  but  spongy  platinum. 

Protiodide  of  Platinum,  PtI. — This  compound  is  prepared 
by  digesting  the  protochloride  of  platinum  with  iodide  of  potas- 


PLATINUM.  437 

sium.  It  is  a  black  powder,  insoluble  in  water  and  alcohol,  and 
unchangeable  by  the  acids.  With  ammonia,  it  forms  the  ammo- 
niacal  iodide  already  described.  At  a  high  heat,  iodine  is 
driven  off. 

Biniodide  of  Platinum.^  Ptig. — When  iodide  of  potassium  is 
mixed  with  perchloride  of  platinum  in  dilute  solution,  the  liquid 
changes  first  to  orange  red,  and  then  to  claret  color,  without 
precipitation ;  but  when  the  solution  is  boiled,  a  black,  some- 
times crystalline  precipitate  subsides,  Avhich  should  be  washed 
with  hot  water,  and  dried  at  a  temperature  not  exceeding  212°. 
It  is  tasteless  and  inodorous,  insoluble  in  water  at  any  tempera- 
ture. It  is  sparingly  soluble  in  alcohol.  Acids  act  feebly  on 
it,  but  it  is  decomposed  by  alkali,  and  begins  to  lose  iodine  at 
270°. 

The  bromides  resemble  the  iodides  both  in  preparation  and 
general  properties. 

OXYSALTS. 

Sulphate  of  Protoxide  cf  Platinum,  PtOjSOj. — This  salt  is 
obtained  by  dissolving  the  recently  precipitated  oxide  of  plati- 
num in  sulphuric  acid.  Like  the  nitrate,  it  forms  a  brown  solu- 
tion. The  combination  with  ammonia,  made  by  precipitating 
the  ammoniacal  chloride  by  nitrate  of  silver,  has  been  already 
alluded  to. 

Sulphate  of  hinoxide  of  platinum  (Pt02,S03)  is  obtained  by 
decomposing  the  bichloride  by  means  of  sulphuric  acid.  It  is 
soluble  and  crystallizable. 

Sulphite  of  protoxide  of  platinum  (PtO,S02)  is  made  by  sus- 
pending the  oxide  in  water,  and  passing  a  stream  of  sulphurous 
acid  gas  through  the  mixture.  It  forms  double  salts  with  soda 
and  ammonia.     There  is  also  a  sulphite  of  the  binoxide. 

Nitrate  of  the  binoxide  of  pilatinum  is  obtained  by  direct  action, 
or  by  double  decomposition  of  the  sulphate  with  nitrate  of  baryta. 
It  forms  basic  double  salts  with  potassa  and  soda. 


438      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


CHAPTER   X. 

MERCURY. 

The  fact  that  an  amalgam  of  mercury  with  other  metals  has 
been  used,  and  is  still  recommended  in  some  quarters  as  a  filling 
for  teeth,  renders  it  necessary  that  a  brief  description  of  this 
metal  should  be  subjoined  to  our  account  of  the  metals  used 
by  the  dentist. 

Mercury  is  found  native,  disseminated  through  the  vein-stone, 
in  mines  of  this  metal.  Sometimes  it  collects  in  such  abundance 
in  hollows  in  the  rock  that  it  may  be  readily  dipped  out.  More 
commonly  it  is  found  as  a  sulphuret,  the  native  cinnabar.  This 
is  occasionally  found  crystallized  in  rhombohedral  prisms  of  an 
adamantine  lustre,  and  a  color  varying  from  cochineal  red  to  a 
reddish  lead  gray.  The  amorphous  variety,  of  a  dull  red  color, 
is  more  frequently  met  with. 

The  principal  mines  of  this  metal  are  those  of  Idria,  in  Aus- 
tria; of  Almaden,  in  Spain;  of  Drei-Konigszug,  in  the  Palati- 
nate ;  and  of  Guancavelica,  in  Peru.  There  are  also  mines  in 
Hungary  and  Bohemia,  the  joint  product  of  which  is  rated  at 
30  or  40  tons  a  year.  Mexico,  Sweden,  China,  Japan,  and 
Chili,  also  contain  mines  of  this  metal. 

The  oldest  of  all  the  mines  is  that  of  Almaden,  in  Spain.  The 
Greeks  imported  cinnabar  from  them  ;  and  Rome,  in  Pliny's  time, 
received  annually  100,000  pounds  of  the  metal  from  the  same 
source.  According  to  Dr.  Ure,  these  mines  employ  a  force  of 
700  miners  and  200  smelters,  and  have  produced,  since  1827, 
200,000  cwt.  of  mercury  a  year.  Some  idea  may  be  formed 
of  their  immense  value  from  the  fact  that,  though  actively 
worked  for  so  many  centuries,  the  mines  are  not  yet  1,000  feet 
below  the  surface.  The  vein  now  worked  is  from  14  to  16  yards 
thick,  and  is  still  thicker  at  the  crossings.  Owing  to  the  bar- 
barous method  of  working,  much  mercury  is  lost,  only  10  per 


MERCURY.  439 

cent,  being  obtained  from  the  ore.  The  geological  formation  is 
an  argillaceous  schist  and  sandstone  grit,  deposited  in  horizontal 
beds,  intersected  occasionally  by  eruptions  of  granite  and  black 
porphyry. 

The  mines  of  Idria,  discovered  in  1497,  are  mined  at  the  depth 
of  280  yards  for  the  bituminous  sulphuret.  Dr.  Ure  says  it 
would  be  easy  to  procure  600  tons  a  year  from  these  mines ;  but 
the  Austrian  government,  in  order  to  keep  up  the  price  of  quick- 
silver, has  limited  its  production  to  one-fourth  of  that  sum.  In 
1803,  a  destructive  fire  broke  out  in  these  mines,  and  was  only 
extinguished  by  inundating  all  the  subterraneous  workings. 
More  than  900  persons  in  the  neighborhood  of  the  mines  suf- 
fered from  nervous  tremblings  and  other  diseases,  generated  by 
the  large  quantity  of  mercury  sublimed  by  the  heat. 

The  mines  of  the  Palatinate  are  numerous,  and  occur  in  va- 
rious geological  formations.  Those  of  Drei-Konigszug  are  the 
most  important.  They  are  worked  at  a  depth  of  more  than  220 
yards,  the  ore  being  a  sandstone  strongly  impregnated  with 
cinnabar.     The  annual  yield  of  these  mines  is  about  30  tons. 

The  mines  of  Guancavelica  yielded,  from  1570,  at  which  time 
they  were  first  opened,  up  to  1800,  53,700  tons  of  metal.  Ac- 
cording to  Ure,  at  the  beginning  of  this  century,  the  annual 
produce  was  from  170  to  180  tons.  The  mercury  is  used  up  in 
the  country  for  amalgamating  gold  and  silver. 

METALLURGIC   TREATMENT   OF   MERCURIAL   ORES. 

The  reduction  of  mercury  from  its  ores  is  a  genuine  dry  dis- 
tillation, which  is  conducted  in  different  modes  at  different 
mines.  A  very  rude  process  is  adopted  in  South  America  and 
in  China.  Wells  or  pits  are  heated  with  a  brushwood  fire,  and 
the  ores  are  thrown  in.  As  they  cool,  the  quicksilver  is  con- 
densed and  collected  from  the  cavities  in  which  it  has  been 
deposited. 

At  Idria,  a  very  extensive  series  of  chambers  communicates 
with  a  large  roasting  kiln,  which  is  divided  into  apartments  by 
three  arches.  The  ores  are  classified  before  being  introduced. 
The  larger  and  richer  bits  are  placed  upon  the  lower  arch.    The 


440      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

second  class,  -which  consists  of  the  smaller  pieces  of  ore,  is  put 
upon  the  second  arch ;  and  the  third  class,  consisting  of  fine 
sand  and  sehlich,  upon  the  highest  arch.  The  strong  oxidating 
flame,  which  plays  over  these  ores,  converts  the  sulphur  into 
sulphurous  acid,  which  escapes,  while  the  liberated  mercury  is 
volatilized  and  gradually  condensed  in  the  chambers. 

Forty  men  are  occupied  three  hours  in  charging  this  furnace, 
which  is  kept,  during  the  ten  or  twelve  hours  the  distillation 
lasts,  at  a  cherry  red  heat.  The  fuel  employed  is  beech-wood. 
A  complete  charge  is  from  1,00()  to  1,200  quintals  of  ore,  which 
yield  from  80  to  90  quintals  of  metallic  mercury.  The  furnace 
requires  five  or  six  days  to  cool,  so  that  but  one  charge  can  be 
worked  in  a  week.  The  furnace  is  180  feet  long,  and  30  feet 
high. 

The  dludel  furnace  is  used  in  Spain.  It  consists  of  a  furnace 
with  one  arch  and  two  chimneys.  One  of  these  is  at  the  same 
end  with  the  fireplace,  and  carries  off  the  greater  portion  of  the 
smoke.  The  other  is  at  the  farther  end,  at  which  the  aludels 
terminate,  and  serves  to  carry  ofi"  the  remaining  smoke.  The 
aludels  are  pipes,  made  by  fitting  into  one  another  a  long  series 
of  earthen  adopters.  These  are  arranged  upon  a  double  inclined 
plane,  and  terminate  in  a  chamber,  which  communicates  with 
the  second  chimney  just  spoken  of.  The  ores  are  placed  upon 
the  arch  and  the  fire  kindled.  As  the  heat  is  raised,  the  mer- 
cury and  the  gases  distil  over  and  pass  through  the  aludels. 
The  greater  portion  of  the  metal  runs  into  a  gutter  provided  for 
its  escape.  Part  remains  in  the  aludels,  and  part  comes  over 
with  the  smoke  and  uncondensed  gases.  This  is  deposited  in 
an  iron  vessel  at  the  bottom  of  the  chamber,  while  the  smoke 
and  gas  pass  out  at  the  second  chimney. 

The  gallery  of  the  Palatinate  is  an  elongated  furnace,  in  which 
are  arranged  rows  of  earthen  retorts  called  cucurbits.  Each  of 
these  communicates  with  a  separate  receiver,  which  is  partly 
filled  with  water.  The  number  for  each  gallery  varies  from  30 
to  62.  Each  cucurbit  is  charged  with  from  56  to  70  pounds  of 
cinnabar,  mixed  with  from  15  to  18  of  quicklime.  The  sul- 
phuret  of  mercury  is  decomposed  by  the  lime,  forming  sulphuret 


MERCURY.  441 

of  calcium  and  sulphate  of  lime,  and  setting  free  metallic  mer- 
cury, which  distils  over. 

Dr.  Ure  erected  at  Landsberg,  in  1847,  an  apparatus  which 
was  a  great  improvement  on  the  old  methods  of  distilling  mer- 
cury. It  consists  of  a  series  of  retorts  like  those  employed  in 
the  manufacture  of  coal  gas.  They  are  set  in  masonry,  and 
each  of  them  is  fitted  at  one  end  with  eduction-pipe,  and,  at  the 
other,  with  an  air-tight  stopper,  closed  by  an  iron  screw.  Con- 
nected with  the  pipes  is  a  large  condenser,  containing  water, 
and  set  in  a  wooden  trough,  also  filled  with  that  fluid.  They 
are  kept  constantly  in  a  uniform  state  of  ignition.  Each  retort 
will  contain  five  hundred  weight  of  ore,  from  which  the  metal  is 
almost  entirely  expelled  in  the  course  of  three  hours. 

MERCURY   AND    ITS   NON-SALINE    COMPOUNDS. 

Mercury. — This  is  easily  distinguished  from  all  other  metals 
by  its  liquidity  at  ordinary  temperatures.  It  is  silver  white, 
with  a  strong  metallic  lustre,  which  it  does  not  lose  when  ex- 
posed to  the  air.  At  39°  it  is  solid,  and  is  then  both  ductile 
and  malleable.  In  polar  latitudes,  mercury  often  freezes,  and 
the  same  result  may  be  attained  in  the  laboratory  by  using  a 
freezing  mixture  composed  of  ether  and  solid  carbonic  acid,  or 
of  pounded  ice  and  crystallized  chloride  of  calcium.  It  may  be 
obtained  in  brilliant  octahedral  crystals,  by  slowly  congealing 
a  quantity  of  it  in  a  platinum  crucible,  arresting  the  process 
before  the  solidification  is  complete,  and  pouring  off  the  liquid 
portion. 

It  expands  with  great  regularity  by  equal  increments  of  heat, 
until  near  its  boiling  point,  680°.  It  volatilizes  far  below  its 
boiling  point,  at  the  ordinary  temperatures  of  the  atmosphere, 
and  even  as  low  as  32°.  This  may  be  proved  by  suspending  a 
sheet  of  gold  leaf  in  the  upper  part  of  a  bottle  containing  mer- 
cury. In  a  few  days  that  portion  of  the  gold  nearest  the  mer- 
cm-y  will  be  whitened,  while  that  at  the  upper  portion  of  the 
bottle  will  be  unaffected,  since  the  vapor  of  mercury  forms  a 
very  shallow  stratum  just  above  the  surface  of  the  metallic  bath. 

The  mercury  of  commerce,  when  obtained  directly  from  the 


442      CHEMISTRY  OP  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

mines,  is  usually  contaminated  only  with  a  little  oxide.  After 
it  has  passed  through  two  or  three  hands,  however,  it  becomes 
abominably  filthy,  being  adulterated  with  a  variety  of  cheap 
metals.  In  consequence  of  this  contamination,  it  tarnishes 
rapidly,  a  gray  film  of  oxide  floating  upon  the  surface. 

It  is  purified  by  repeated  distillation,  but  is  hardly  ever  obtained 
absolutely  pure  by  this  process  alone,  some  of  the  impurities 
invariably  passing  over  into  the  receiver.  To  remove  these,  the 
mercury  is  treated  with  common  nitric  acid,  diluted  with  about 
twice  its  volume  of  distilled  water.  The  whole  is  then  heated 
to  about  110°  F.,  and  nitrate  of  suboxide  of  mercury  will  be 
rapidly  formed.  This  nitrate  and  the  free  acid  react  on  the 
foreign  metals  present,  which  are  held  in  solution  in  the  form  of 
salts.  Any  oxide  of  mercury  originally  present  is  dissolved  by 
the  nitric  acid.  This  action  is  to  be  continued  for  twenty-four 
hours,  the  mixture  being  repeatedly  agitated.  The  water  is  now 
evaporated,  and  the  nitrate,  which  remains  as  a  crystalline  crust 
on  the  surface  of  the  mercury,  skimmed  ofl".  The  metallic  mer- 
cury is  washed  with  distilled  water,  and  dried  under  a  bell-glass, 
over  a  saucer  of  caustic  lime. 

Strong  hydrochloric  acid  does  not  affect  mercury,  even  though 
boiled  upon  it.  Dilute  sulphuric  acid  fails  to  dissolve  it,  but 
the  concentrated  acid,  aided  by  heat,  attacks  it  violently.  Nitric 
acid  acts  very  energetically  upon  it,  even  in  the  cold,  and,  when 
moderately  diluted  with  water,  binoxide  of  nitrogen  is  plentifully 
evolved. 

The  specific  gravity  of  mercury  at  78.8°  is  13.530 ;  at  47°, 
13.545  ;  while  that  of  frozen  mercury  is  15.612.  The  specific 
gravity  of  its  vapor  is  6.976.  Its  symbol  is  Hg.  Its  atomic 
weight  has  been  recently  changed,  and  with  it  the  nomenclature 
of  its  compounds.  According  to  Berzelius,  it  is  1265.828  on 
the  oxygen,  and  101.266  on  the  hydrogen  scale.  Swanberg 
makes  it  1250.9  on  the  former,  and  100.07  on  the  latter. 

Oxides.  Suboxide  of  Mercury,  HgjO. — This,  which  was 
formerly  called  the  protoxide,  is  a  brownish-black  powder,  de- 
composing by  light  and  warmth  into  oxygen  and  the  metal, 
and  giving  up  its  oxygen  to  deoxidating  agents  generally.     It 


I 


MERCURY.  443 

is  obtained  by  treating  one  of  its  salts  or  the  subchloride  with 
caustic  alkali,  washing  and  drying. 

It  is  a  feeble  base.  The  soluble  salts  are  colorless ;  the  basic 
salts  yellow,  and  generally  soluble.  Caustic  alkalies ^give  with 
these  salts  a  black  precipitate ;  iodide  of  potassium,  a  yellow 
olive  green  ;  chromate  of  potassa,  a  deep  crimson  ;  and  sulphu- 
retted hydrogen,  a  black  precipitate. 

Oxide  of  3Iercury,  HgO. — This  oxide,  known  as  red  oxide, 
red  precipitate,  or  deutoxide,  is  formed  by  decomposing  the 
nitrate  through  the  agency  of  heat.  It  is  a  red  crystalline  and 
shining,  or  amorphous  and  dull  powder,  decomposed  in  the  same 
manner  as  the  suboxide.     Heated  with  sulphur,  it  explodes. 

Its  salts  are  colorless  ;  yellow,  if  basic  ;  acid  in  their  reac- 
tion ;  styptic  in  their  taste,  and  poisonous  in  their  quality. 
Caustic  alkali  throws  down  an  orange  red ;  carbonates,  a  brown- 
ish-red ;  ammonia,  a  white ;  solution  of  galls,  a  yellow ;  chro- 
mate of  potassa,  an  orange  red  ;  iodide  of  potassium,  a  brilliant 
red ;  sulphuretted  hydrogen,  a  black,  a  white,  or  a  red  precipi- 
tate, according  to  the  quantity  of  the  reagent. 

SuLPHURETS.  Subsulphuret  of  3Iercury,  Hg^S. — This  sulphu- 
ret  is  prepared  by  passing  a  stream  of  sulphuretted  hydrogen 
through  a  solution  of  nitrate  of  the  suboxide.  It  is  a  black  pow- 
der, which  is  oxidized  by  digestion  in  strong  nitric  acid.  Heat 
resolves  it  into  sulphuret  and  metallic  mercury. 

Sulphuret  of  Mercury^  HgS- — This  substance  occurs  native 
as  cinnabar.  It  is  also  prepared  artificially,  and  constitutes  the 
beautiful  pigment,  vermilion.  It  is  made  by  fusing  sulphur  and 
mercury  together,  and  volatilizing  the  resulting  cinnabar,  or  by 
treating  Ethiops  mineral  with  a  warm  solution  of  potassa. 

Etliiops  mineral  was  supposed  by  Brande  to  be  a  mixture  of 
sulphur  and  the  sulphuret.  It  is  made  by  rubbing  mercury  and 
sulphur  together. 

Plwspliuret  of  mercury,  HgP,  is  black,  when  formed  by  digest- 
ing mercury  and  phosphorus  with  water ;  orange  yellow,  when 
made  by  passing  phosphuretted  hydrogen  over  the  dry  chloride. 

Nitruret  of  mercury,  NHgj,  is  a  dark  brown,  highly  explosive 
powder,  made  by  heating  the  red  oxide  saturated  with  ammonia. 


444      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


AMALGAMS. 

The  alloys  of  mercury  "with  other  metals  have  received  the 
name  of  amalgams.  They  are  made  by  mixing  the  metals  to- 
gether in  the  cold,  either  alone  or  with  some  compound  "which 
favors  their  union.  The  fluid  amalgams  are  solutions  of  the 
genuine  amalgams  in  excess  of  mercury.  The  more  solid  amal- 
gams are  crystalline,  and  so  soft  as  to  be  capable  of  being 
kneaded. 

Of  the  numerous  amalgams  "which  have  been  made,  but  a  few 
are  in  general  use.  That  employed  for  the  electrical  machine  is 
composed  of  mercury  50,  tin  25,  zinc  25.  The  silvering  for 
mirrors  is  a  mixture  of  mercury  30,  tin  70.  Glass  globes  are 
silvered  with  a  compound  of  mercury  80,  bismuth  20.  Gilders' 
amalgam  contains  10  parts  of  gold  to  90  of  mercury,  while  that 
for  silvering  is  composed  of  15  parts  of  silver  to  85  of  gold. 

Amalgams  of  mercury  with  silver,  gold,  and  other  metals,  have 
been  used  for  the  purpose  of  filling  teeth.  The  deleterious 
effects  of  such  fillings  will  be  presently  examined.*  One  of  the 
vilest  combinations  of  this  class  is  that  made  by  mixing  together 
9  parts  of  mercury,  17  of  tin,  45.5  of  bismuth,  and  28.5  of 
lead. 

HALOID    SALTS. 

SuhcTiloride  of  Mercury,  Hg^Cl. — This  is  the  compound  long 
known  as  calomel.  It  has  also  been  called  protochloride,  di- 
chloride,  mild  chloride,  and  submuriate.  It  is  prepared  by  inti- 
mately mixing  4  parts  of  the  chloride  with  3  of  metallic  mercury, 
subliming  and  washing  thoroughly  to  free  it  from  corrosive 
sublimate.     It  occurs  native  as  horn  quicksilver. 

It  is  insoluble  in  water  ;  decomposed  by  contact  with  many 
of  the  metals,  by  heating  with  sulphur  and  some  sulphurets,  or 
with  sulphuric,  nitric,  or  muriatic  acid,  by  subliming  it  with  sal 
ammoniac  ;  in  all  which  cases  the  chloride  is  formed.  Treated 
with  a  solution  of  potassa  or  soda,  it  yields  the  suboxide,  and 

*  See  Effects  of  Mercury  on  the  System. 


MERCURY.  445 

under  caustic  ammonia  it  forms  a  black  subchloramide  of  mer- 
cury. Chloride  of  sodium  assists  its  solution,  and  as  this  alka- 
line salt  is  always  found  in  the  stomach,  we  are  no  longer  un- 
der the  necessity  of  supposing  calomel  to  undergo  a  gradual 
metamorphosis  into  corrosive  sublimate  previous  to  arbsorption. 

Chloride  of  Mercury^  HgCl. — This  intensely  corrosive  poison 
is  formed  by  crystallization  from  a  solution  of  the  red  oxide  or 
of  calomel  in  hydrochloric  acid.  It  crystallizes  in  opaque 
rhombic  prisms. 

At  563°  it  fuses  and  volatilizes,  the  specific  gravity  of  its 
vapor  being  9420.  Exposed  to  the  rays  of  the  sun,  its  solution 
is  decomposed,  oxygen  escapes,  hydrochloric  acid  is  formed,  and 
subchloride  of  mercury  precipitated.  It  is  decomposed  by  seve- 
ral metals,  by  sulphur,  phosphorus,  and  their  lower  acids. 
Potash  throws  down  from  its  solution  a  brown  oxychloride  of 
mercury. 

Vegetable  and  animal  albumen  form  with  it  a  white  insoluble 
precipitate,  a  compound  of  calomel  and  albumen.  Consequently, 
albumen,  in  one  form  or  another,  commonly  as  white  of  egg,  has 
been  recommended  and  largely  used  as  an  antidote  to  this  poison. 
Mialhe  prefers  the  moist,  recently  precipitated  sulphuret  of  iron, 
which  immediately  decomposes  the  chloride  of  mercury. 

The  chloride  of  mercury  enters  into  combination  with  a  great 
variety  of  substances,  forming  many  double  salts,  which  do  not 
require  special  examination  in  this  place. 

Bromides. — Bromine,  like  chlorine,  forms  with  mercury  two 
salts,  one  insoluble,  analogous  to  calomel,  the  other  soluble,  like 
corrosive  sublimate. 

Iodides. — The  suhiodide  is  a  greenish-yellow  powder,  easily 
decomposed  by  light,  made  by  mixing  200  parts  of  mercury  with 
126  parts  of  iodine  •moistened  with  alcohol,  and  extracting  the 
excess  of  iodine  with  alcohol. 

The  iodide  is  a  fine  red  powder,  obtained  by  precipitating  a 
salt  of  the  red  oxide  by  an  alkaline  iodide.  It  sublimes  in  bril- 
liant red  quadratic,  or  in  yellow  right  rhombic  crystals. 

The  fivx)ride  is  an  orange  yellow  powder. 


446      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 


OXYSALTS. 

A.  Salts  of  Black  Oxide.  Suhsulphate  of  Mercury,  Ilg^OSOj. 
— This  is  obtained  by  heating  mercury  with  oil  of  vitriol,  till 
all  the  metal  disappears  and  a  white  powder  takes  its  place. 
This  is  dissolved  in  boiling  water,  from  which  it  crystallizes. 

Nitrate  of  the  Suboxide  of  Mercury.  Protonitrate  of  Mercury ^ 
Hg^ONOj+SHO. — This  salt  crystallizes  from  a  solution  of  mer- 
cury in  excess  of  cold  nitric  acid.  Water  decomposes  it  into 
a  basic  salt.  When  kept  in  a  laboratory  as  a  chemical  reagent, 
it  must  always  have  some  metallic  mercury  in  the  bottom  of  the 
bottle. 

The  phosi^liate  Is  a  white  crystalline  powder,  insoluble  in  phos- 
phoric acid  and  decomposed  by  heat.  It  is  fornlfed  by  double 
decomposition. 

B.  Salts  of  Red  Oxide.  Sulphate  of  Oxide  of  Mercury^ 
HgOS03. — When  5  parts  of  sulphuric  acid  are  heated  with  4  of 
mercury,  a  dry  crystalline  mass,  the  sulphate  of  the  red  oxide, 
is  formed.  Water  decomposes  it  into  a  soluble  salt  and  a  yellow, 
nearly  insoluble,  basic  salt,  the  turpeth  mineral  of  the  older 
chemists.  A  number  of  compound  salts  are  formed  from  this 
sulphate. 

Nitrate  of  Oxide  of  3Iercury. — The  neutral  salt  is  known  only 
in  solution,  from  which  a  basic  salt  crystallizes.  By  treating  the 
crystals  with  water  warmed  to  different  temperatures,  two  basic 
salts,  one  yellow  and  the  other  brown,  are  formed.  This  salt 
also  forms  numerous  double  salts  with  ammonia,  and  with  other 
substances. 

The  phosphate  is  white,  insoluble  in  water,  but  soluble  in  phos- 
phoric acid  and  ammoniacal  salts.  The  earbotiate  is  a  pale  red, 
insoluble  powder. 

The  other  salts  do  not  demand  special  attention  here. 

EFFECTS   OF   MERCURY   ON   THE   SYSTEM. 

The  general  influence  of  mercury  upon  the  system  is  so  well 
known,  that  we  need  not  do  more  than  glance  at  its  more  promi- 
nent features. 


MERCURY.  447 

The  ordinary  alterative  action  of  this  metal  when  adminis- 
tered in  properly  regulated  doses,  is  attended  by  no  especial 
disturbance  of  the  system.  But  at  times  it  does  not  operate 
upon  the  economy  with  such  tranquillity.  A  febrile  condition, 
or  at  least  a  state  approximating  fever,  is  not  uncornmon.  At 
such  times  the  surface  becomes  warm,  the  circulation  is  accele- 
rated, the  pulse  is  frequent  and  jerking,  the  face  is  slightly 
flushed,  the  nervous  impressibility  is  heightened  ;  in  short,  there 
is  a  general  excitement  of  all  the  functions.  The  glandular  sys- 
tem is  especially  acted  on  ;  the  liver  secretes  more  bile,  the 
salivary  glands  eliminate  more  saliva ;  and  in  this,  as  well  as  in 
the  green  discharges  from  the  bowels,  the  metal  may  be  detected. 

When  mercury  is  about  to  spend  its  force  upon  the  glands  of 
the  mouth,  the  earliest  indication  of  its  action  is  an  unpleasant 
metallic  taste  like  that  of  copper  or  brass.  Presently,  the  gums 
become  sore  and  tender,  the  mucous  membrane  is  inflamed,  the 
teeth  suff'er  with  disagreeable  sensations,  which  are  referred  to 
the  fangs,  and  these  are  raised  to  actual  pain  when  the  jaws  are 
firmly  closed.  Presently,  the  gums  swell  and  become  spont^y, 
then  a  whitish  line  is  seen  along  the  edge  of  the  teeth,  and  the 
peculiar  mercurial  fetor  is  developed.  The  salivary  glands  are 
swollen  and  hot,  the  jaws  stiff"  and  painful.  After  this  condition 
of  things  has  lasted  a  short  time,  a  copious  flow  of  saliva  takes 
place.  The  disease  does  not  always  stop  here.  The  cheek  is 
puff'ed  out  with  a  red  swelling,  which  gradually  becomes  more 
and  more  livid,  till  a  gangrene  sets  in  which  sweeps  it  away, 
slough  after  slough  laying  bare  the  cavity  of  the  mouth,  and 
hurrying  the  unhappy  suff'erer  to  the  grave.  Sometimes  the 
ulcerations  attack  the  gums,  break  them  down,  seize  upon  the 
periosteum,  penetrate  the  bone,  which  becomes  carious  and 
spongy,  and  finally  exfoliates,  leaving  the  most  hideous  gaps  in 
the  face.  At  other  times,  this  ulceration  or  gangrene  extends 
among  the  soft  parts,  and  opens  the  bloodvessels,  giving  rise  to 
the  most  destructive  hemorrhage. 

Nor  is  its  influence  by  any  means  confined  to  the  cavity  of 
the  mouth.  With  or  without  salivation,  it  exerts  the  most  bane- 
ful influence  over  the  economy.  At  times,  it  acts  as  a  powerful 
and  dangerous  sedative  to  the  circulation.     The  countenance 


448      CHEMISTRY  OF  METALS  AND  EARTHS  USED  BY  THE  DENTIST. 

becomes  pale  and  anxious,  the  pulse  small  and  frequent.  There 
is  much  anxiety  about  the  praecordia,  great  nervous  agitation, 
and  extreme  and  alarming  prostration  of  strength. 

At  other  times,  an  eruption  breaks  out  over  the  surface,  which 
has  been  called  hydrargyria^  eczema  mercuriale,  and  lepra  mer- 
eurialis. 

The  most  distressing  effects  it  produces,  however,  are  the 
affections  of  the  nervous  system.  These  are  especially  expe- 
rienced by  those  who  contract  the  poison  by  slow  and  gradual 
absorption  of  the  metal.  One  of  the  most  frequent  of  these  dis- 
orders is  a  form  of  paralysis  agitans.  The  tremors  of  the  limbs 
are  so  considerable  that  the  patient  is  unable  to  walk  without 
staggering,  or  to  hold  anything  in  his  hand.  He  stammers,  and 
finds  it  extremely  difficult  to  speak  at  all.  His  memory  fails 
him,  his  intellect  becomes  weak,  and  his  sight  is  dimmed.  Such 
phenomena  as  these  are  constantly  met  with  among  gilders, 
looking-glass  makers,  and  workmen  in  quicksilver  mines. 

So  virulent  a  poison  as  this  should  never,  except  in  cases  of 
the  sternest  necessity,  be  introduced  into  the  system,  and  then 
it  should  be  done  with  the  greatest  care,  and  so  managed  that 
its  absorption  may  be  controlled,  or  that  the  quantity  to  be 
taken  in  may  be  regulated. 

How  are  these  conditions  fulfilled  when  an  amalgam  is  intro- 
duced into  a  tooth?  Not  at  all.  The  secretions  of  the  mouth 
float  around  the  metal,  and  act  upon  it.  An  important  part  is 
also  played  by  the  other  constituents  of  the  filling,  which, 
together  with  the  mercury,  form  a  galvanic  apparatus,  greatly 
accelerating  the  solution  of  this  metal. 

The  amalgam  question,  as  it  has  been  called,  is  thus  answered 
with  the  utmost  promptitude  by  chemistry.  To  the  chemist,  it 
has  but  one  side ;  it  needs  but  to  be  stated  to  be  immediately 
decided  upon.  The  use  of  a  mercurial  amalgam  is,  under  all 
circumstances,  wrong;  for  the  simple  reason  that  we  have  no 
guarantee  that  the  most  frightful  results  of  mercurial  poisoning 
will  not  take  place.  The  introduction  of  lead  into  it,  as  in  the 
villanous  compound,  of  which  a  formula  has  been  given,  is  a  step 
farther  into  the  wrong. 

That  the  metal  itself,  as  well  as  its  salts,  is  capable  of  pro- 


MEKCURY.  449 

ducing  these  symptoms,  is  a  matter  of  such  commonplace  noto- 
riety that  the  veriest  tyro  is  familiar  with  it.  That  a  soluble 
compound  is  formed  in  the  mouth,  which  can  be  absorbed  by  the 
teeth,  is  proved  by  simple  inspection  of  a  tooth  which  has  been 
filled  with  it.  I  have  seen  the  metallic  discoloration  extending 
into  the  fang. 

The  dose  of  mercury  which  produces  its  peculiar  effects  is  well 
known  to  be  extremely  variable.  The  probability  is  that,  except 
in  rare  cases,  but  a  small  portion  of  it  ever  gets  access  at  any 
one  time  into  the  economy.  The  effect  experienced  is  not  that 
of  the  last  dose,  however  large,  but  of  all  that  has  effected  a 
lodgement  in  the  tissues.  The  recent  observations  of  Melsens 
and  Budd  have  shown  that  both  mercury  and  lead,  even  in  the 
form  of  insoluble  salts,  may  remain  a  long  while  combined,  as  it 
were,  with  the  tissues,  producing  varied  phenomena  of  disease, 
and  then  may  be  set  free  by  iodide  of  potassium,  so  as  to  enter 
the  blood  and  produce  their  specific  primary  efi'ects  upon  the 
organism.  Now,  if  these  insoluble  compounds  are  capable  of 
producing  so  much  mischief,  by  what  possible  process  of  reason- 
ing can  any  one  arrive  at  the  conclusion  that  metallic  mercury, 
which  we  all  know  to  be  soluble  in  the  fluids,  will  prove  inert? 
If  it  be  urged  that  the  smallness  of  the  quantity  and  the  gradual 
nature  of  the  absorption  is  a  guarantee  against  poisoning,  a 
reply  is  to  be  found  in  the  well-known  fact  that  small  portions 
of  metallic  mercury,  daily  absorbed,  produce  the  most  distress- 
ing and  unmanageable  forms  of  mercurial  poisoning.  It  is  pre- 
cisely in  this  manner  that  the  workmen  in  mercury  introduce 
the  metal  into  their  systems.* 

*  As  an  example  of  the  remarkably  small  quantity  of  a  metal  which  is 
sometimes  sufficient  to  poison,  a  case  recently  reported  to  the  American 
Medical  Association,  and  copied  in  nearly  all  the  journals,  may  be  cited. 
The  most  obstinate  and  protracted  symptoms  of  lead  poisoning  occurred  in 
a  gentleman  who  had  been  in  the  habit  of  cheiving  metallic  lead. 


29 


PART    II. 

THE    MATERIALS    USED    IN    MAKING    INCORRUPTIBLE 

TEETH. 


CHAPTER   I. 


SILICON. 

The  basis  of  all  glass  or  porcelain  is  silicic  acid,  which  is 
itself  an  oxide  of  an  elementary  body,  silicon.  Davy  was  the 
first  to  demonstrate  this,  by  bringing  the  vapor  of  potassium  in 
contact  with  pure  silicic  acid  heated  to  whiteness.  Silicate  of 
potassa  was  formed,  and  silicon  was  found  diffused  through  it 
in  the  form  of  black  particles  like  plumbago.  It  was  then  taken 
for  a  metal  and  called  silicium.  Thomson,  however,  regarded 
it  as  a  metalloid,  and  classified  it  with  carbon  and  boron ;  and 
this  opinion  has  received  the  sanction  of  the  great  name  of 
Berzelius.  The  latter  chemist  first  obtained  this  substance  pure 
in  1824. 

The  Swedish  philosopher  procured  it  by  the  action  of  potas- 
sium on  fluosilicic  acid  gas.  It  is  more  conveniently  obtained, 
however,  from  the  double  fluoride  of  silicon  and  potassium,  or 
sodium  previously  dried  at  a  temperature  approaching  that  of 
redness.  Ten  parts  of  silicofluoride  of  potassium  are  mixed 
with  from  8  to  9  of  potassium  in  an  iron  or  glass  tube,  and  the 
potassium  fused  and  stirred  with  the  salt.  It  is  then  heated 
with  a  spirit-lamp ;  the  temperature  becomes  suddenly  raised  to 
ignition  by  the  energetic  action  of  the  potassium  on  the  silica, 
the  base  of  which  is  alloyed,  as  it  were,  with  the  potassium. 


SILICON.  451 

On  throwing  the  brown  mixture  into  water,  silicon  separates, 
and  fluoride  of  potassium  and  potassa  are  left  in  solution.  It 
is  washed  thoroughly,  first  in  cold  and  then  in  hot  water,  till 
everything  soluble  is  taken  up. 

Another  mode  of  obtaining  it  is  to  expose  the  chloride  of 
silicon  to  heat  in  a  tube,  so  arranged  that  the  vapor  of  this 
substance  shall  pass  over  potassium,  air  having  first  been  expelled 
from  the  apparatus.  The  excess  of  the  chloride  having  been 
driven  oiF,  after  the  union  of  the  potassium  with  the  chlorine, 
the  whole  is  put  into  water,  and,  chloride  of  potassium  having 
been  dissolved  out,  silicon  remains. 

As  thus  procured,  silicon  is  a  dark  nut-brown  powder,  which 
does  not  stain  the  fingers.  It  is  a  non-conductor  of  electricity. 
It  exists  in  two  distinct  forms,  like  its  oxide,  which  also  has 
two  modifications. 

The  first  of  these  is  insoluble  in  any  of  the  strong  acids  except 
the  hydrofluoric.  It  is  soluble  in  caustic  potassa.  It  burns 
readily  and  vividly  in  the  air,  and  more  vividly  in  oxygen  gas. 
The  result  of  this  combustion  is  a  coating  of  silicic  acid,  which 
protects  the  centre  from  the  farther  action  of  the  air. 

This  inner  portion  is  found,  on  removing  the  superficial  coat, 
to  be  completely  changed  in  its  properties.  It  is  now  no  longer 
combustible,  even  in  oxygen  gas.  It  is  darker  and  denser  than 
before,  so  that  it  sinks  in  oil  of  vitriol.  It  resists  the  action  of 
hydrofluoric  acid  and  potassa,  and  is  unaltered  when  ignited 
with  nitrate  of  potassa.  It  is  soluble,  however,  in  nitro- hydro- 
fluoric acid. 

The  symbol  of  silicon  is  Si ;  its  combining  number,  according 
to  Berzelius,  22.185  on  the  hydrogen,  and  227.312  on  the 
oxygen  scale. 

Silicic  Acid,  SiOj.  30.155. — Silica,  or  silicic  acid,  is  abund- 
antly difi"used  throughout  nature.  It  forms  the  chief  portion  of 
most  of  the  simple  minerals,  and  gives  lustre  and  hardness  to 
the  greater  number  of  gems.  These  are,  indeed,  nothing  but 
salts  of  this  widely  distributed  acid.  In  quartz,  rock  crystal, 
chalcedony,  feldspar,  sandstone,  and  other  bulky  rocks,  it  is  the 
principal  ingredient.  It  may  be  obtained  of  sufficient  purity 
for   ordinary   purposes   by   igniting   transparent   rock-crystal, 


452         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

quenching  it  in  water  when  fully  incandescent,  and  reducing 
the  crumbling  mass  to  powder. 

To  obtain  it  perfectly  pure,  it  is  necessary  to  fuse  quartz, 
feldspar,  or  some  of  the  silicious  minerals  with  four  times  its 
weight  of  carbonate  of  soda  or  potassa,  or  a  mixture  of  both. 
The  resulting  glassy  mass  is  then  dissolved  in  pure  hydrochloric 
acid,  evaporated  to  dryness,  digested  in  hydrochloric  acid,  and 
then  thoroughly  washed,  first  with  dilute  hydrochloric  acid, 
afterwards  with  water. 

Silicic  acid  exists  in  two  distinct  modifications.  The  first 
variety  is  largely  soluble  in  water,  and  is  obtained  by  dissolving 
a  soluble  silicate  in  hydrochloric  acid,  or  by  oxidating  the 
sulphuret  of  silicon  in  water.  It  then  appears  as  a  bulky,  gelati- 
nous hydrate,  converting  a  large  quantity  of  fluid  into  a  tremu- 
lous jelly,  soluble  both  in  water  and  acid,  and  partially  decom- 
posed by  simple  drying,  but  losing  all  its  water  only  after 
ignition. 

Evaporation  to  dryness  converts  this  hydrate  into  the  second 
modification.  This  is  totally  insoluble  in  water  or  acids.  It  is 
a  white  gritty  powder,  communicating  a  rough  and  dry  sensation 
to  the  fingers  when  rubbed  between  them.  It  is  insipid  and 
inodorous.  It  is  infusible  at  the  highest  heat  of  a  furnace,  but 
melts  readily  to  a  clear  glass,  which  may  be  drawn  out  in  threads, 
before  the  oxyhydrogen  blowpipe.  When  this  fused  silica  is 
dropped  into  water,  it  becomes  so  very  hard  as  to  indent  a  steel 
pestle  and  mortar.  It  is  volatile  in  the  vapor  of  water,  for 
steam  passed  through  tubes  containing  silica  heated  to  white- 
ness deposits,  on  cooling,  large  quantities  of  it  as  a  snow-white 
powder. 

At  common  temperatures,  it  is  a  feeble  acid,  but,  at  a  high 
heat,  it  expels  most  acids  from  their  salts.  With  the  fixed 
alkalies,  it  forms  substances  which  vary  with  the  relative  pro- 
portions of  the  ingredients  used.  These  are  obtained  by  fusing 
silica  with  the  carbonate  of  the  alkali.  Violent  ebullition  takes 
place  in  consequence  of  the  rapid  escape  of  carbonic  acid  gas, 
and  a  vitreous  substance  results,  which  is  rather  soluble,  if  the 
alkali  has  been  to  the  silica  as  three  to  one.  The  solution  which 
was  formerly  called  liquor  silicum,  has  an  alkaline  reaction,  and 


SILICON.  453 

absorbs  cai^bonic  acid  from  the  atmosphere,  becoming  partially 
decomposed.  Concentrated  acids  precipitate  the  silica  as  the 
gelatinous  hydrate  already  described.  Reversing  the  proportions 
of  the  ingredients,  we  obtain  the  well-known  hard,  insoluble 
silicate,  glass. 

Sulphuret  of  Silicon,  ^\'&y — This  substance,  which  is  obtained 
by  heating  silicon  in  the  vapor  of  sulphur,  is  white,  earthy, 
decomposed  by  moist  air  or  water,  with  the  formation  of  sulphu- 
retted hydrogen  and  the  soluble  modification  of  silicic  acid. 

Cldoride  of  Silicon,  SiClj. — When  a  stiff  paste,  made  of  finely 
powdered  silica,  oil,  and  charcoal,  is  first  charred  in  a  close  cru- 
cible, and  then  pulverized  and  ignited  in  a  porcelain  tube  while 
a  stream  of  chlorine  gas  passes  over  it,  a  new  substance  is  formed, 
which  may  be  condensed  in  a  cooled  receiver.  It  is  the  chloride 
of  silicon,  a  very  volatile  liquid,  boiling  at  122°,  with  a  very 
pungent  acid  odor,  fuming  in  the  air,  and  decomposing  in  water 
into  hydrochloric  and  silicic  acids. 

Bromide  of  Silicon,  SiBr3,  is  made  like  the  former,  substitut- 
ing bromine  for  chlorine.  It  is  a  fuming,  colorless  liquid,  boiling 
at  about  300°,  and  freezing  at  from  5°  to  10°. 

Hydrofluo silicic  Acid,  2SiF3,HF. — When  equal  parts  of  finely 
powdered  fluor  spar  and  sand  or  pounded  glass  are  heated  in  a 
retort  with  six  parts  of  sulphuric  acid,  a  gas,  fluosilicic  acid,  is 
formed,  which  may  be  collected  in  'perfectly  dry  vessels  over 
mercury.  Should  this  gas  be  transmitted  through  water,  the 
liquid  becomes  gelatinous  in  consequence  of  the  deposition  of 
silica ;  and,  on  being  filtered  from  the  silicic  acid,  a  clear  solu- 
tion of  hydrofluosilicic  acid  is  obtained. 

This  acid  is  a  useful  reagent  in  the  laboratory,  serving,  among 
other  purposes,  to  separate  baryta  from  strontia. 


454        MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 


CHAPTER    II. 

ALUxAIINUM. 

Alumina  is  also  a  very  abundant  substance  in  nature,  and  is, 
like  silica,  an  oxide.  Davy  first  demonstrated  this  by  passing 
the  vapor  of  potassium  over  alumina  heated  to  whiteness,  thus 
deoxidating  the  earth  and  procuring  metallic  aluminum. 

Wohler  obtained  it  in  sufficient  quantity  to  examine  its  pro- 
perties by  mixing  chloride  of  aluminum  with  potassium  in  a 
platinum  crucible,  and  heating  it  over  a  spirit-lamp.  The  ac- 
tion is  so  violent  that  sudden  ignition  takes  place,  and  the 
crucible  becomes  redhot.  The  substances  are  generally  found 
to  have  been  completely  fused.  After  the  crucible  has  thoroughly 
cooled,  the  gray  fused  mass  is  Avell  washed  in  water,  the  chloride 
of  potassium  being  taken  up,  and  gray  metallic  aluminum  in 
powder  and  spangles  remaining.  Liebig  obtained  aluminum  by 
introducing  the  chloride  into  a  closed  bent  tube,  and  placing 
near  it,  in  the  horizontal  limb,  some  fragments  of  metallic  potas- 
sium, so  that  when  the  chloride  is  heated,  its  vapor  shall  pass 
over  the  metal.  The  same  action  takes  place  as  in  the  last- 
named  process,  and  the  chloride  of  potassium  is  removed  from 
the  aluminum  in  the  same  way. 

It  is  a  gray  powder,  resembling  platinum,  containing  scales 
or  spangles  of  a  metallic  lustre,  and  a  few  small  spongy  masses, 
white  and  bright,  like  metallic  tin.  For  fusion,  it  requires  a 
temperature  higher  than  that  at  which  cast-iron  is  liquefied.  By 
this  means,  or  by  strong  pressure,  the  powder  just  described  is 
condensed,  and  possesses  a  strong  and  decided  metallic  lustre. 
In  its  finely  divided  state,  it  does  not  conduct  electricity,  though 
when  fused  or  pressed,  it  behaves  towards  this  imponderable 
like  other  metals. 

Heated  to  redness  in  the  air,  it  burns  with  a  vivid  light,  and 
is  oxidated  to  alumina.     Sprinkled  in  the  flame  of  a  candle, 


ALUMINUM.  455 

brilliant  sparks  are  given  off  like  those  emitted  by  iron  when 
burnt  in  oxygen  gas.  Heated  to  redness  in  pure  oxygen,  it 
burns  with  a  vivid  light  and  intense  heat.  The  resulting  alumina 
is  partially  vitrified,  of  a  yellowish  color,  and  hard  enough  to 
cut  glass.  It  is,  in  fact,  an  artificial  corundum.  Heated  nearly 
to  redness  in  an  atmosphere  of  chlorine,  it  takes  fire,  and  chloride 
of  aluminum  is  sublimed. 

Aluminum  is  not  oxidated  by  water  at  common  temperatures, 
nor  is  its  lustre  tarnished  by  lying  in  water  during  its  evapora- 
tion. When  the  water  is  heated  to  the  boiling  point,  a  little 
hydrogen  gas  escapes,  and  the  metal  is  slowly  oxidated;  though 
even  after  protracted  ebullition,  the  smallest  particles  suffer 
scarcely  any  change. 

The  symbol  of  aluminum  is  Al;  its  atomic  weight  13.72  on 
the  hydrogen,  and  171.17  on  the  oxygen  scale.  This  is  calcu- 
lated from  the  chemical  analogy  of  alumina  with  sesquioxide  of 
iron,  so  that  it  too  is  rated  as  a  sesquioxide. 

Sesquioxide  of  Alumina,  Al^Og.  Alumina. — This  oxide  is 
found  everywhere  over  the  surface  of  the  earth.  Feldspar,  the 
slates,  the  clays,  and  many  other  of  the  great  mountain  and 
alluvial  masses,  consist  to  a  great  extent  of  this  earth.  It  is 
found  pure  and  crystallized  in  corundum,  the  varieties  of  which 
are  adamantine  spar,  topaz,  ruby,  sapphire,  &c.  It  is  extremely 
hard,  transparent,  and  lustrous. 

Artificially,  it  is  obtained  by  a  variety  of  methods.  The 
easiest  of  these  is  to  ignite  pure  ammoniacal  alum,  when  the 
volatile  alkali  and  the  sulphuric  acid  are  driven  off,  leaving  the 
pure  alumina.  Berzelius  obtained  it  by  precipitating  a  solution 
of  alum  with  an  excess  of  carbonate  of  soda  or  of  potassa,  and 
digesting  the  precipitate  for  some  time  in  the  precipitant;  wash- 
ing it  well,  dissolving  it  in  hydrochloric  acid,  filtering,  precipi- 
tating with  ammonia,  and  igniting.  Liebig  throws  down  the 
sulphuric  acid  from  alum  by  chloride  of  barium.  Chlorides  of 
potassium,  aluminum,  and  barium  remain  in  solution.  He  fil- 
ters, and  evaporates  to  dryness,  ignites  the  remainder,  and 
washes  out  the  chlorides  with  water. 

As  thus  obtained,  it  is  a  white,  loose,  soft,  inodorous,  and 
insipid  powder.     After  strong  ignition,  it  contracts,   and  be- 


456         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

comes  sufficiently  hard  to  strike  fire  with  steel.  It  is  infusible 
at  the  highest  furnace  heats,  but  melts  before  the  oxyhydrogen 
jet  more  easily  than  silica.  Gaudin  fused  it  to  a  bead  the  size 
of  a  hazelnut,  which  contained  in  its  cavity  crystals  of  corun- 
dum. It  has  a  powerful  affinity  for  water,  attracting  it  from 
the  air,  and  forming  with  it  a  paste  which  is  quite  plastic,  and 
can  be  wrought  into  a  variety  of  forms.  When  once  moistened, 
it  will  not  part  with  its  water  at  a  heat  short  of  whiteness.  It 
contracts  or  shrinks  in  proportion  as  water  is  expelled.  Upon 
this  property  is  founded  the  old  pyrometer  of  Wedgewood. 

It  has  a  double  set  of  affinities,  so  that  it  appears  alternately 
to  act  the  part  of  an  acid  and  an  alkali.  It  forms  salts  on  the 
one  hand  with  the  acids,  and  on  the  other,  combines  with  the 
alkalies.  Potassa  readily  dissolves  it,  so  do  the  acids,  even  the 
acetic.  It  changes  its  character,  however,  after  ignition,  when 
it  becomes  extremely  difficult  to  dissolve  it. 

It  is  the  basis  of  all  porcelain  and  pottery  wares  as  well  as 
of  brick.  Its  affinity  for  colors  also  renders  it  a  most  useful 
agent  to  the  dyer  in  fixing  his  tints  upon  vegetable  fibre. 

Aluminum  combines  with  sulphur,  phosphorus,  tellurium,  &c. 
but  these  compounds  possess  so  little  general  interest  that  we 
shall  pass  them  by  without  description. 

Chloride  of  Aluminum^  AICI3. — This  compound  is  obtained 
by  passing  a  stream  of  chlorine  over  a  mixture  of  alumina  and 
charcoal  heated  to  redness  in  a  porcelain  tube.  It  is  of  a  citron 
yellow  color,  translucent,  crystalline,  and  stratified  like  talc.  It 
is  fusible,  volatile,  and  very  soluble  in  alcohol.  It  forms  double 
salts  with  the  alkaline,  and  even  with  sulphuretted  and  phos- 
phuretted  hydrogen. 

Bromine  and  fluorine  combine  with  aluminum. 

The  oxysalts  of  alumina  are  numerous  and  important  from 
their  various  applications  to  the  arts. 

Sidphate  of  Alumina^  Al^OjSSOj. — This  is  the  formula  of  the 
neutral  sulphate,  which  crystallizes  in  thin,  flexible,  pearly 
leaves,  needles,  and  tables.  There  are  several  basic  sulphates. 
The  double  sulphates  with  the  alkalies  are  also  numerous.  The 
most  important  of  these  is  the  double  sulphate  of  alumina  and 
potassa,  commonly  called  alum.     This  salt  is  transparent,  color- 


POTASSIUM.  457 

less,  crystallizing  in  octahedra,  combined  with  cubes  and  dodeca- 
hedra,  tlie  edges  and  pyramids  being  replaced  by  planes. 

/Silicates  of  Alumina. — There  are  numerous  native  and  artifi- 
cial combinations  of  this  kind,  both  simple  and  double.  Kaolin, 
for  example,  is  2(Al203,Si03)  +  3Ag.  Kyanite  is  2Al203,Si03,  or 
3Al203,2Si03.  Potash  feldspar  is  KO,Si03+Al203,Si03.  The 
formula  for  soda  feldspar  is  the  same,  substituting  Na  for  K.  The 
micas  are  complex  double  silicates.  We  shall  return  to  this 
subject  again  in  a  future  chapter. 


CHAPTER   III. 

POTASSIUM. 

Potash  being  an  important  ingredient  in  the  spar  which  is 
used  in  the  manufacture  of  porcelain,  a  brief  account  of  its  chemi- 
cal history  is  inserted  here. 

Its  name  is  derived  from  the  manner  in  which  it  was  first 
obtained,  by  boiling  down  the  leachings  of  wood-ashes  in  iron  pots. 
The  Germans  call  it  kalium,  a  name  which  they  get  from  the 
Arabic  words  al  kali,  or  the  kali,  which  term  was  originally  ap- 
plied to  the  ashes  of  sea-weeds.  At  first  no  distinction  was 
made  between  it  and  soda,  but  about  the  middle  of  the  last  cen- 
tury, it  was  shown  to  be  a  different  substance  from  the  latter, 
and  the  names,  vegetable  and  mineral  alkali,  were  applied  to 
the  two  oxides. 

Potassium. — In  1807,  Davy  showed  that  potash  was  an  oxide  of 
the  metal  potassium,  by  decomposing  the  alkali  through  the  agency 
of  a  powerful  galvanic  battery.  Gay-Lussac  and  Thenard  after- 
wards obtained  it  by  igniting  potash  and  iron  turnings  in  an 
iron  tube.  Wohler's  modification  of  Brunner's  plan,  is  to  ignite 
a  mixture  of  charred  cream  of  tartar  and  charcoal  in  a  wrought- 
iron  flask,  which  is  laid  horizontally  in  the  fire,  an  iron  tube 
being  screwed  in  the  opening.  The  receiver  consists  of  two 
copper  vessels,  the  lower  one  open  above  and  the  upper  one  below, 


458         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

and  so  arranged  that  the  naphtha  with  which  the  bottom  one  is 
one-third  filled,  shuts  out  the  air  from  the  upper  vessel.  This 
has  three  openings  towards  its  upper  part,  into  one  of  which  the 
tube  is  passed.  Opposite  it,  is  another,  closed  by  a  cork,  which 
is  from  time  to  time  removed,  so  as  to  thrust  in  an  iron  wire 
or  auger,  to  clean  out  the  tube  when  it  happens  to  be  stopped 
up.  The  third  opening  is  designed  for  the  escape  of  gases,  and 
may  be  furnished  with  a  tube,  passing  into  a  condenser,  so  as  to 
collect  the  arsenic  acid.  The  flask,  being  charged  with  the  mix- 
ture already  described,  is  now  heated,  and  when  green  vapors 
begin  to  show  themselves,  the  tube  is  connected  with  the  receiver, 
and  a  strong  heat  applied.  The  tube  must  be  bored,  whenever 
it  becomes  clogged,  and  should  this  be  impossible,  the  heat 
should  be  abated,  for  if  an  attempt  should  be  made  to  open  it, 
the  ignited  potassium  would  be  driven  out  with  an  explosion. 
The  operator  must,  therefore,  stand  on  one  side,  and  have  his 
hands  covered.  When  the  operation  is  completed,  the  receiver 
is  detached,  all  the  openings  being  immediately  stopped  with 
corks.  As  soon  as  it  has  cooled  sufficiently,  the  inner  vessel  is 
removed,  its  contents  moistened  with  naphtha,  and  the  potassium 
raked  down  into  the  naphtha.  The  black  mass  is  either  dis- 
solved to  obtain  rhodizonate  and  croconate  of  potassa,  or  re- 
distilled in  a  fresh  operation.  The  metal  is  purified  by  redistil- 
lation.    It  is  always  kept  in  naphtha. 

Potassium  is  a  brilliant  white  metal,  having  a  crystalline  texture. 
Pleische  obtained  it  in  cubic  crystals.  It  is  a  soft  solid,  begin- 
ning to  melt  at  70°,  and  becoming  completely  fluid  at  136°.  At 
50°  it  is  like  wax  in  consistence,  and  at  32°  it  becomes  brittle. 
In  close  vessels  it  sublimes  in  crystals.  In  the  air  it  rapidly 
oxidates,  becoming  white  and  moist.  Thrown  on  water  it  takes 
fire  from  the  violence  of  the  action,  and  burns  with  a  violet 
light.  Its  affinity  for  oxygen  is  so  powerful  that  it  abstracts 
this  metalloid  from  nearly  all  its  compounds. 

The  specific  gravity  of  potassium  is  0.865.  Its  symbol  is  K. 
Its  combining  number  is  39.11  on  the  hydrogen,  488.856  on  the 
oxygen  scale. 

Potassa,  KO.  47.11. — When  potassium  is  heated  in  the  air, 
dry  potash  is  obtained.     The  hydrates  are  numerous.    The  most 


POTASSIUM.  459 

important  is  the  protohydrate,  which  is  commonly  obtained  by 
treating  pearlash  with  lime.  To  procure  a  pure  hydrate  of  potash, 
it  is  necessary  to  make  a  solution  of  3  parts  of  pure  carbonate 
of  potash  in  12  parts  of  distilled  water,  and  to  add  to  it,  while 
boiling,  in  small  quantities  at  a  time,  milk  of  lime,  made  by 
slaking  2  parts  of  caustic  lime  with  6  of  water.  It  is  boiled 
after  each  addition  of  lime,  and  finally,  when  all  is  added,  boiled 
for  fifteen  minutes.  A  little  is  then  filtered  ofi".  Should  it 
give  no  precipitate  with  lime-water,  it  may  be  regarded  as  pure. 

Should  a  cloudiness  be  produced  by  this  reagent,  we  are  ap- 
prised that  some  carbonate  of  potash  has  been  left  undecom- 
posed,  and  the  whole  is  to  be  again  boiled  with  milk  of  lime. 
When  all  the  carbonate  has  been  decomposed,  the  liquid  is  ra- 
pidly filtered,  so  as  to  expose  it  as  little  as  possible  to  the  air. 
Donovan's  apparatus  supplies  a  simple  and  very  efficient  means 
of  accomplishing  the  desired  result  of  excluding  air  as  much  as 
possible.  When  operating  on  large  quantities,  the  clear  solu- 
tion is  siphoned  off  from  the  sediment,  and  boiled  in  a  clean 
iron  kettle  to  the  consistence  of  an  oil.  Should  it  become 
cloudy,  it  is  again  drawn  off  and  allowed  to  settle  in  closely 
corked  bottles  ;  and,  the  clear  solution  being  returned  to  the 
pots,  the  concentration  goes  on.  The  oily  liquid  is  then  evapo- 
rated in  a  silver  dish  till  white  vapors  begin  to  rise  from  it.  It 
is  then  poured  into  moulds,  or  on  slabs,  when  it  is  solidified. 
During  the  evaporation,  carbonate  is  formed,  which  floats  on  the 
oily  liquid,  and  may  be  skimmed  off.  It  may  also  be  obtained 
by  treating  sulphate  of  potassa  with  pure  baryta  water,  and 
evaporating  as  just  described. 

The  ordinary  potash  of  the  shops,  however  beautiful  and  white 
it  may  look,  always  contains  some  chloride,  and  occasionally  a 
little  carbonate.  It  is  made  of  pearlash,  which  is  never  an 
absolutely  pure  carbonate. 

Fused  potassa  [potassa  fusa,  lapis  causticus,  or  caustic  pot- 
ash of  the  shops)  is  the  protohydrate  of  potash,  containing  84 
per  cent,  of  dry  potassa.  It  is  the  form  in  which  this  alkali  is 
usually  seen,  and  was  formerly  supposed  to  be  pure  and  anhy- 
drous. It  is  perfectly  undecomposable  in  all  known  heats.  It 
fuses  below  redness,  and  volatilizes  at  higher  heats.     It  has  a 


460         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

powerful  affinity  for  water,  deliquescing  rapidly  in  the  air,  and 
dissolving  in  one-half  its  weight  of  water  with  the  evolution  of 
heat.  Even  when  quite  dilute,  it  has  a  peculiar  smooth,  soapy 
feel,  when  rubbed  between  the  fingers.  This  is  due  to  its  action 
on  the  epidermis,  the  scales  of  which  it  dissolves. 

In  the  solid  form,  potassa  is  a  powerful  escharotic,  and  is 
largely  used  by  the  surgeon.  The  dentist  occasionally  employs 
it  for  the  destruction  of  the  exposed  nerves  of  the  teeth.  Its 
action  is  violent,  and  accompanied  with  much  pain.  This  may 
be,  to  some  extent,  moderated,  by  making  it  into  a  paste  with 
alcohol  and  morphia. 

Our  space  does  not  permit  us  to  dwell  upon  the  other  non- 
saline  compounds  of  potassium.  Of  the  salts,  there  are  few  of 
special  interest  to  us.     We  shall  describe  only  the 

Nitrate  of  Potassa^  K0,N05. — This  salt  is  generated  spon- 
taneously in  some  soils,  and  crystallizes  upon  their  surface.  It 
is  easily  obtained  from  them  by  lixiviating  them  and  crystallizing 
the  clear  solution.  The  East  Indies  yield  the  greatest  portion 
of  this  substance,  though  it  occurs  elsewhere  in  soils.  It  is 
more  commonly  found  native  as  an  efflorescence  on  certain  rocks, 
and  as  a  saline  crust  in  caverns.  In  Tennessee  and  Kentucky, 
especially  in  the  latter  State,  native  nitre  is  so  abundant  in 
caverns  as  already  to  have  become  a  considerable  article  of 
traffic. 

Some  plants  have  the  property  of  generating  nitre  from  the 
constituents  of  ordinary  soils.  Among  these  is  tobacco ;  and 
few  persons  have  resided  any  length  of  time  in  a  tobacco-growing 
country  who  have  not  observed  crystals  of  this  salt  occasion- 
ally formed  in  the  axils  of  the  leaves.  Maize  is  also  said  to 
form  it. 

The  formation  of  nitre  in  soils,  and  on  the  surface  of  rocks, 
has  been  variously  explained.  It  has  been  supposed  that  the 
animal  matter  present  in  soil  and  calcareous  rock  becomes 
oxidated  at  the  expense  of  the  atmosphere,  so  that  its  nitrogen 
is  converted  into  nitric  acid.  Deliquescent  nitrates  of  lime  and 
magnesia  result ;  and  these,  in  their  turn,  are  decomposed  by 
the  potash  which  is  present  in  the  soil.     This  generation  of 


POTASSIUM.  461 

nitre,  both  in  soils  and  rocks,  is  limited  to  a  very  small  distance 
from  the  surface  of  porous  stones. 

Dr.  John  Davy  and  M.  Longchamp  suppose  that  azotized 
matter  is  not  absolutely  necessary ;  but  that  the  oxygen  and 
nitrogen  of  the  atmosphere,  when  condensed  by  capillary  force, 
combine  in  the  proportions  necessary  to  produce  nitric  acid, 
which,  when  formed,  attacks  the  magnesia  and  lime,  and  is 
afterwards  abstracted  from  the  salts  of  these  bases  by  potash. 
They  believe  the  action  of  the  porous  limestones  and  the  water 
in  them,  in  this  case,  to  be  analogous  to  that  of  spongy  platinum 
in  condensing  oxygen  and  hydrogen  into  water;  or  of  sesquioxide 
of  iron  and  argillaceous  substances  in  combining  nitrogen  and 
hydrogen  to  form  ammonia.  Plausibility  is  given  to  this  opinion 
by  the  fact  that,  in  India,  Spain,  and  other  nitre-producing 
countries,  this  salt  is  generated  in  places  remote  from  all  human 
habitations,  and,  to  all  appearance,  secluded  as  completely  as 
possible  from  all  organic  influences. 

During  the  wars  of  the  French  Revolution,  England,  having 
possession  of  the  sea,  shut  out  from  the  ports  of  France  all  the 
Indian  and  other  foreign  nitre.  This  struck  at  the  nation's 
vital  part,  by  cutting  off  the  supply  of  the  most  important  muni- 
tion of  war.  The  genius  of  the  French  chemists,  however,  over- 
came the  diflSculty  by  establishing  artificial  nitre-beds,  from 
which  the  manufactories  of  gunpowder  Avere  liberally  supplied. 

These  nitrieres  artificielles  are  made  by  using  as  the  basis  a 
light,  porous  earth,  freely  permeable  by  atmospheric  air,  and 
containing  a  large  proportion  of  carbonate  of  lime  or  old  mortar 
rubbish.  This  is  interstratified  with  beds  of  dung,  five  or  six  inches 
thick,  and  the  whole  mass  raised  into  a  truncated  pyramid,  which 
is  kept  moist  by  constant  watering.  When  the  whole  has  been 
decomposed  into  a  sort  of  mould,  it  is  placed  in  layers  under  a 
shed,  watered  with  urine  and  the  drainings  of  the  stable-yard, 
taking  care  not  to  soak  them  so  much  as  to  obstruct  the  free 
entrance  of  atmospheric  air,  and  at  the  same  time  to  keep  them 
moist  enough  to  furnish  ample  means  for  the  absorption  and 
combination  of  the  atmospheric  gases.  The  beds  are  freely 
turned  over  thoroughly  to  mix  their  contents  and  to  favor  the 
combination  of  the  nascent  acid  with  the  bases.     Two  years  are 


462         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

necessary  to  complete  the  process,  during  the  latter  six  months 
of  which  period  the  organic  liquids  are  disused  and  pure  water 
substituted  in  the  watering  process.  Longchamp  suggests  that 
this  manufacture  be  carried  on  in  forests,  where  fuel  and  labor 
are  cheap,  that  organic  matters  be  disused,  and  that  tuf  be 
employed  to  condense  the  gases. 

Most  of  the  indigenous  nitre  of  France  is  obtained  from  old 
mortar  and  plaster,  especially  that  of  the  ground-floor  and  cel- 
lars. This  is  lixiviated  in  large  casks,  and  the  solution  obtained 
from  their  lixiviation  is  evaporated  and  mixed  with  sufficient 
wood-ashes  to  substitute  potash  for  lime  as  a  basis  of  the  nitrates. 
The  chloride  of  sodium  collects  on  the  surface  during  the  con- 
centration of  the  nitre,  and  is  skimmed  off  in  ladles.  The 
concentrated  solution  is  siphoned  off,  crystallized,  and  purified 
sufficiently  for  commercial  purposes  by  one  or  two  recrystalliza- 
tions. 

Nitrate  of  potash  is  a  colorless  salt,  crystallizing  in  six-sided 
prisms  with  dihedral  summits.  They  are  grooved,  and  in  the 
cavities  are  liable  to  contain  mother  water.  The  specific  gravity 
varies  from  1.93  to  2.  Its  taste  is  cool  and  saline.  It  is  in- 
odorous, permanent  in  the  air  when  pure,  fusible  at  662°,  con- 
creting from  the  fluid  into  a  solid  mass,  with  a  coarsely  radiating 
fracture,  which  has  received  the  names  of  sal  prunelle  and 
mineral  crystal.  If  the  heat  be  raised  to  ignition,  a  portion  of 
the  salt  is  decomposed,  oxygen  being  given  off,  and  nitrite  of 
potassa  remaining.  Owing  to  this  property,  it  is  a  powerful 
oxidating  agent  in  metallurgy.  For  the  same  reason,  it  defla- 
grates violently  on  ignited  coals,  when  heated  to  redness  with 
sulphur.  It  is  soluble  in  7  parts  of  water  at  32° ;  in  about  3|- 
at  60°;  in  less  than  half  a  part  at  194° ;  and  in  four-tenths  at 
212°. 

It  is  a  substance  of  almost  universal  application  in  the  arts. 
It  is  essential  to  the  manufacture  of  gunpowder,  of  sulphuric 
and  nitric  acids,  and  of  flint-glass.  It  is  used  also  in  medicines, 
and  in  many  chemical  and  pharmaceutical  operations. 


SODIUM.  463 


CHAPTER    IV 


SODIUM. 


There  are  soda  as  well  as  potassa  feldspars,  so  that  a  brief 
account  of  the  behavior  of  soda  is  here  inserted. 

Sodium,  as  well  as  potassium,  was  discovered  by  Sir  Hum- 
phry Davy,  in  1807.  It  is  obtained  in  the  same  manner  as 
potassium,  which  it  resembles  in  color,  lustre,  and  mode  of  crys- 
tallization. At  common  temperatures,  it  is  so  soft  that  it  may 
be  formed  into  leaves  by  the  pressure  of  the  fingers.  At  4°  F., 
it  is  hard  ;  at  32°,  malleable;  at  122°,  very  soft ;  at  194°,  fluid, 
and  at  a  red  heat,  vaporizable.  It  oxidates  readily  in  the  air, 
though  not  so  rapidly  as  potassium.  It  is  rapidly  oxidated  by 
water,  throwing  off  hydrogen  and  steam.  In  hot  water,  it  scin- 
tillates, but  does  not  burn  like  potassium.  Ducatel  says  that  the 
heat  rises  high  enough  to  inflame  the  sodium,  even  in  cold 
water,  provided  the  metal  be  confined  to  one  place,  and  the 
water  rest  on  a  non-conducting  base,  like  charcoal. 

The  specific  gravity  of  sodium  is  0.972.  Its  symbol  is  Na; 
its  combining  number,  23.3  on  the  hydrogen,  and  289.729  on 
the  oxygen  scale. 

Soda,  NaO.  31.3. — Dry  soda,  absolutely  anhydrous,  is  made 
by  burning  the  metal.  It  is  a  gray  mass,  which  fuses  at  a  strong 
red  heat,  and  absorbs  water  greedily  with  evolution  of  heat. 

Hydrate  of  Soda,  NaO, HO. — Water  added  to  dry  soda  is 
rapidly  absorbed,  and  hydrate  is  formed.  It  is  usually  obtained 
by  the  action  of  caustic  lime  upon  the  best  soda-ash.  The  two 
substances  are  mixed  in  the  proportion  of  48  parts  of  quicklime 
to  every  100  of  alkali  present  in  the  ash.  It  is  a  white,  brittle, 
fibrous  substance,  fusible  and  slightly  volatile  at  a  full  red  heat. 
It  may  be  obtained  in  crystals  by  evaporating  a  concentrated 
solution  at  a  very  low  temperature. 

The  salts  of  soda  are  numerous  and  interesting,  but  our  limits 


464         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

will  suffice  only  for  the  description  of  the  two  which  are  chiefly 
used  as  fluxes,  the  carbonate  and  the  borate. 

Carbonate  of  Soda,  NaOjCOg. — The  impure  carbonate  of  soda 
of  commerce,  called  soda-ash,  is  obtained  from  common  salt  by 
a  somewhat  complicated  process.  The  salt  is  first  decomposed 
by  the  action  of  sulphuric  acid  at  a  high  temperature.  Hydro- 
chloric acid  is  given  ofi",  and  sulphate  of  soda  remains.  The 
sulphate  is  powdered  and  mixed  thoroughly  with  excess  of  chalk, 
or  carbonate  of  lime,  and  some  charcoal,  also  in  fine  powder. 
The  mixture  is  then  fused,  and  ball-soda,  or  crude  soda,  is  ob- 
tained, which  is  a  mixture  of  carbonate  of  soda,  and  caustic  soda 
with  sulphuret  of  calcium,  carbonate  of  lime,  charcoal,  undecom- 
posed  sulphate,  &c.  This  crude  soda  is  lixiviated  in  a  series  of 
cisterns,  so  arranged  that  the  lowermost  shall  contain  a  concen- 
trated solution  of  the  alkaline  carbonate,  while  the  higher  shall 
have  in  it  nearly  pure  water,  to  exhaust  the  last  remains  of 
alkali  from  the  crude  mass.  The  lye  of  the  lowest  cistern  is 
concentrated,  during  which  process  it  lets  fall  crystals  of  car- 
bonate of  soda.  These  are  lifted  out  and  drained,  while  the  re- 
maining liquid,  which  contains  caustic  soda  and  sulphuret  of 
sodium,  is  evaporated  to  dryness,  mixed  with  charcoal  or  sawdust, 
and  heated  in  a  reverberatory  furnace  till  all  the  sulphuret  is 
decomposed.  Sometimes  the  crystals  are  not  separated,  but  the 
whole  solution  is  evaporated  to  dryness,  and  treated  as  just  de- 
scribed.    The  resulting  compound  is  the  soda-ash  of  commerce. 

From  this  the  pure  carbonate  is  obtained  by  repeated  crys- 
tallizations. Its  crystals  always  contain  water,  the  amount  of 
which  varies  with  the  temperature  at  which  the  crystallization 
has  been  eflFected.  For  the  purposes  of  fluxing,  this  water  should 
be  expelled  by  heating  the  crystals  to  a  low  redness  in  a  per- 
fectly clean  wrought-iron  crucible.  A  snowy-white  agglutinated 
mass  is  obtained,  which  is  easily  reduced  to  an  impalpable  pow- 
der. In  this  form,  it  is  one  of  the  most  valuable  reagents,  in 
the  dry  way,  possessed  by  the  chemist,  and  one  of  the  most  im- 
portant of  all  the  metallurgist's  fluxes.  It  possesses  the  power 
of  decomposing  the  silicates,  the  silicic  acid  of  which,  at  a  high 
heat,  unites  with  the  alkali,  expelling  the  carbonic  acid.  Dur- 
ing the  fusion,  the  escape  of  the  last-named  acid,  in  a  gaseous 


SODIUM.  465 

form,  causes  a  violent  ebullition,  which  will  throw  out  all  the 
contents  of  the  crucible,  if  the  latter  is  not  sufficiently  capacious. 
When  this  ebullition  has  ceased,  and  the  surface  of  the  melted 
mass  has  become  bright  and  smooth,  the  fusion  is  complete. 
Besides  this,  carbonate  of  soda  forms  fusible  compounds  with 
most  of  the  metallic  oxides,  and  retains  in  suspension,  without 
losing  its  fluidity,  a  great  number  of  infusible  substances,  such 
sa  charcoal  and  the  earths.  This  substance  also,  at  a  high 
temperature,  oxidates  some  metals.  The  carbonic  acid  which 
it  contains  is  partially  decomposed  into  carbonic  acid,  which 
escapes,  and  oxygen,  which  combines  with  the  metal. 

Borates  of  Soda. — There  are  two  borates  of  soda,  the  neutral 
borate  (NaO,B03)  and  the  biborate  (NaO,2B03).  The  latter  is 
the  salt  used  as  a  flux. 

The  biborate  of  soda  is  manufactured  from  the  native  boracic 
acid  formed  in  such  abundance  in  the  lagoons  of  Tuscany,  or  is 
imported  as  a  crude  impure  article,  under  the  name  of  tincal, 
from  Asia  and  South  America.  The  crude  boracic  acid  from 
the  lagoons,  is  saturated  with  carbonate  of  soda,  and  crystallized 
at  92°.  Repeated  crystallizations  purify  the  salt.  If  these  are 
made  at  a  temperature  lower  than  130°,  the  crystals  assume  the 
form  of  oblique  rectangular  prisms.  If  crystallized  at  130°, 
octahedral  borax  is  obtained,  mixed  with  the  common  crystals. 

Borax  has  an  alkaline  reaction,  and  a  cool,  faintly  saline  taste. 
"When  exposed  to  the  air,  the  superficial  layer  of  its  crystals 
loses  water  and  effloresces.  Heated  moderately,  it  loses  water, 
and  is  greatly  increased  in  bulk,  being  converted  into  a  loose, 
light,  white  mass.  If  the  heat  be  now  increased,  it  fuses 
gradually  to  a  transparent  colorless  glass.  To  one  or  the  other 
of  these  forms  it  should  be  reduced,  before  it  is  used  as  a  flux  ; 
otherwise  its  property  of  swelling,  as  it  loses  its  water,  would 
be  productive  of  great  inconvenience,  and  might  even  completely 
defeat  the  object  of  the  manipulator.  The  glass  is  the  best 
form  of  flux,  and  it  has  the  advantage  also  of  keeping  better, 
as  it  does  not  absorb  water  from  the  air  so  readily  as  the  loose, 
spongy  variety. 

Borax  has  been  called  a  universal  flux,  and  it  fully  deserves 
the  appellation.     It   forms  fusible  compounds  with  silica  and 
30 


466         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

nearly  all  the  bases.  Its  solvent  power  and  that  of  its  acid 
have  recently  been  made  use  of  to  obtain  artificial  silicious, 
and  other  earthy  crystals. 


CHAPTER    V. 

THE  MATERIALS  USED  FOR  PORCELAIN  TEETH. 

CLAYS. 

The  clays  constitute  a  very  extensive  geological  formation. 
Clay,  or  aluminous  minerals  bearing  that  name,  enter  into  the 
composition  of  many  of  the  older  rocks,  but  those  used  in  the 
arts  are  of  modern  formation.  These  strata  are  characterized 
by  a  very  minute  division  of  their  particles,  and  a  want  of 
solidity.  They  are  easily  suspended  in  water,  with  which  they 
form  a  dough,  and  it  is  to  this  property  we  owe  their  very 
general  distribution.  They  have,  in  all  cases,  been  deposited 
from  still  or  running  water.  Their  origin  has  undoubtedly  been 
from  disintegrated  rocks.  In  many  places,  the  process  of  the 
formation  and  deposit  of  clays  may  be  seen  even  now  going  on. 
Porcelain  clay,  or  kaolin,  being  found  surrounded  by  the  rocks, 
from  which  it  was  formed,  offers  the  most  favorable  opportunity 
for  the  solution  of  the  problem  of  the  formation  of  these 
deposits. 

It  was  first  ascertained  that  all  species  of  kaolin  were  formed 
by  the  decomposition  of  feldspathic  minerals  by  the  atmosphere. 
On  examining  the  kaolin,  however,  a  manifest  diversity  in  the 
physical  character  of  its  component  parts  was  discovered.  A 
portion  of  it  only  was  the  real  plastic  elay^  as  it  is  termed.  The 
rest  was  found  to  consist  of  fragments  of  undecomposed  rock, 
of  free  silicic  acid,  and  silicates  of  the  alkaline  earths.  The 
rocky  debris  may  consist  of  substances  capable  of  generating 
clay,  but  which  have  not  been  suflBciently  disintegrated,  or  of 
earths  which  cannot  undergo  that  transformation.    There  is  also 


CLAYS.  467 

a  soluble  silica  present,  which  has  combined  with  bases  during 
the  process  of  decomposition. 

To  examine  porcelain  earth,  therefore,  the  soluble  silica  must 
first  be  removed,  by  boiling  it  for  a  minute  or  two  with  a  solu- 
tion of  potash  containing  about  20  per  cent,  of  the  alkali.  The 
clay  can  then  be  separated,  by  boiling  it  first  with  sulphuric  acid 
and  afterwards  with  potash.  The  alumina,  together  with  the 
alkalies  and  earths,  when  they  are  present,  is  held  in  solution 
by  the  sulphuric  acid,  and  the  silica  by  the  potash,  the  unde- 
composed  rocks  remaining  as  residue.  The  clay,  rejecting 
the  earths,  is  found  to  be  composed  according  to  the  formula 
M203,Si034-2Aq,  in  which  M  represents  the  metallic  base, 
usually  aluminum.  Feldspar  has  the  formula  M203,3Si03  4- 
MOjSiOj,  the  letter  M  representing  usually  potash,  soda,  or 
an  alkaline  earth.  A  comparison  of  the  formulae,  will  throw 
light  on  the  processes  concerned  in  the  formation  of  porcelain 
earth: — 

Feldspar  =  M203+4Si03+KO  is  decomposed  into  porcelain- 
clay  =  M203+Si03,  into  an  insoluble  silicate  of  potash  = 
SSiOj+KO,  when  the  feldspar  contained  potash,  or  silicate  of 
soda  =  SSiOj+NaO,  when  soda  was  the  base  of  the  mineral. 

These  silicates  are  still  farther  decomposed ;  the  latter  parts 
with  SiOg,  and  becomes  the  soluble  bisilicate  of  soda,  NaO,2Si03, 
while  from  three  equivalents  of  the  former,  SKOjOSiOj,  the  same 
amount  of  silica  is  separated,  leaving  the  soluble  compound, 
3KO,8Si03.  In  time,  these  soluble  salts  are  removed  by  the 
action  of  water.  The  rapidity  with  which  this  will  be  effected, 
will  depend,  of  course,  upon  the  length  of  time  the  clay  has 
been  subjected  to  these  decomposing  agencies,  and  the  freedom 
with  which  the  water  has  had  access  to  it.  The  alkaline  earths, 
if  present  in  the  rocks,  are  usually  found  mixed  up  with  the 
clays. 

An  examination  of  a  very  large  number  of  specimens  of 
kaolin,  leads  to  the  adoption  of  the  formula  Al203,Si03-f2Aq 
for  the  great  majority  of  these  clays.* 

Clay  is,  as  we  have  already  said,  pulverulent  when  dry,  and 

*  Knapp's  Chemical  Technology. 


468         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

emits  a  peculiar  odor,  termed  argillaceous,  when  breathed  on. 
When  moistened,  it  forms  a  mass,  communicating  usually  an 
unctuous  sensation  to  the  touch,  and  capable  of  being  moulded 
into  almost  any  desired  form.  When  dried,  it  shrinks  very 
much,  and  usually  cracks,  as  may  be  seen  in  any  sun-baked 
clayey  soil.  When  dried  at  ordinary  temperatures,  water  can 
again  convert  it  into  the  same  soft  yielding  mass.  When 
exposed  to  a  very  intense  white  heat,  it  does  not  fuse,  but  all 
its  characters  are  changed.  It  is,  indeed,  still  porous,  and 
continues  to  absorb  water,  but  this  liquid  has  no  longer  any 
action  upon  it.  Its  particles  now  adhere  strongly  to  one  another, 
and  it  becomes  hard  and  sonorous.  Laurent  has  shown  that 
clay  goes  on  increasing  in  density  till  it  arrives  at  a  cherry  red 
heat,  and  that  after  that  its  specific  gravity  diminishes,  till  at 
an  intense  white  heat  it  is  no  higher  than  it  was  at  212°  F. 

These  properties  of  the  clay  will,  of  course,  be  modified,  and 
often  seriously  impaired  by  the  foreign  matters  which  are  usu- 
ally found  in  them.  The  variety  of  these  foreign  substances 
has  already  been  mentioned.  In  a  yellow  clay  of  Denmark,  of 
granitic  origin,  Foschhammer  found,  in  the  granite,  feldspar, 
quartz,  mica,  magnetic  iron,  oxide  of  titanium,  and  compounds 
of  cerium;  in  the  clay,  kaolin,  sand,  mica,  oxides  of  iron  and 
titanium,  and  compounds  of  cerium. 

Here  the  clay  came  from  the  feldspar,  but  was  mingled  with 
the  quartz  or  sand  and  with  the  mica,  while  the  magnetic  iron 
was  farther  oxidated,  and  mixed  with  the  titanium  and  cerium 
present  in  the  granite. 

Among  these  foreign  substances,  those  which  exert  the  most 
unfavorable  influence  over  the  clay  are  sand  (composed  of  quartz 
and  decomposed  minerals),  iron,  lime,  and  inagnesia.  They 
all  diminish  its  plasticity,  sand  interfering  with  it  the  most,  and 
iron  the  least.  Lime  or  iron  mixed  with  clay,  entirely  changes 
its  relations  to  heat.  It  becomes  fusible,  and  melts  with  greater 
or  less  readiness,  as  it  contains  more  or  less  of  these  ingredients. 
Magnesia  has  little  eff"ect  upon  clay,  and  sand  diminishes  its 
fusibility,  as  well  as  the  extent  of  its  contraction. 

Broguiart  has  divided  the  clays  into  four  varieties:  the  fire- 
proof, the  fusible,  the  effervescing  or  calcareous,  and  the  ferru- 


CLAYS. 


469 


ginous  or  ochrey.  Of  these,  there  is  but  one  variety  to  which 
we  need  direct  our  attention  at  present,  the  fire-proof. 

Kaolin,  or  Porcelain  Earth. — The  name  kaolin  is  the  Chinese 
hao  lin  or  hauling,"^  and  has  been  adopted  in  all  European  lan- 
guages. It  is  an  earthy,  white  or  grayish  mineral,  easily  pul- 
verized, and  containing  usually  foreign  substances  mixed  with 
it.  It  is  friable  in  the  hand,  and  is  with  some  difficulty  formed 
into  a  paste  with  water.  It  is  usually  found  in  primitive  moun- 
tain districts,  among  blocks  of  granite  rich  in  feldspar,  but  poor  in 
mica,  upon  porphyry  and  the  more  recent  feldspathic  rocks.  In 
consequence  of  this  origin,  most  of  the  kaolins  contain  a  few 
spangles  of  mica  diffused  through  them,  not  to  be  separated  by 
washing. 

The  principal  localities  of  kaolin,  on  the  eastern  continent, 
are,  in  Asia — China  and  Japan ;  in  Europe — St.  Yrieux-la-perche, 
near  Limoges  and  Bayonne,  in  France;  Miessen,  Halle,  and 
Passau,  in  Germany;  and  St.  Anstle,  Cornwall,  in  England. 
In  the  United  States,  kaolin  has  been  found  near  Wilmington 
and  Newcastle,  in  Delaware,  and  in  Chester  County,  Pennsyl- 
vania. It  also  occurs  at  Andover,  Massachusetts ;  and  abundantly 
in  New  Milford,  Kent,  and  Cornwall,  Connecticut ;  and  in  Essex 
and  Warren  counties,  New  York.  Good  kaolin  is  also  found  in 
the  vicinity  of  Baltimore. 

The  kaolin  of  St.  Yrieux,  used  in  the  famous  manufactory 
of  Sevres,  has  been  found  by  Berthier  to  contain  in  the  100 
parts : — 


Silica 

47.09 

Alumina    . 

36.41 

Potash 

1.56 

Magnesia  . 

2.94 

Water 

12.00 

The  Cornish  China  clay  is  artificially  prepared  by  passing  a 
stream  of  water  over  decomposed  granite.  This  carries  off  the 
finer  particles  of  feldspar,  which  are  received,  together  with  the 

*  Meaning  liigJi  ridge,  the  name  of  a  hill  near  Jauchan  Fu,  where  this 
mineral  is  obtained.  Fe-tiin-fze,  with  which  the  Chinese  mix  their  kaolin 
for  their  porcelain  manufactures,  is  a  quartzose  feldspathic  rock,  consisting 
mainly  of  quartz. 


470 


MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 


water,  in  cisterns  or  ponds,  where  the  mineral  is  allowed  to  sub- 

.side.     The  water  is  then  drawn  off,  and  the  fine  sediment  is 

removed,  and  exposed  to  the  atmosphere  for  four  or  five  months, 

when  it  is  ready  for  use.     Richardson's  analysis  of  a  specimen 


this  clay  gave — 

Silica 46.32 

Alumina    . 

39.74 

Protoxide  of  iron 

.27 

Lime 

.36 

Magnesia 

.44 

Water  and  some  alkali 

12.67 

Loss          .... 

.20 

100.00 

From  a  table  of  analysis  by  Brogniart  and  Malaguti,  pub- 
lished in  Knapp's  Chemical  Technology,  we  extract  the  following 
estimate  of  the  clays  of  Newcastle  and  Wilmington: — 

Wilmington,  Newcastle. 
Rocky  portion  insoluble  in  potash 

and  acid  ....         22.81  34.99 

Lime,  magnesia,  and  potash         .  1.14 

Soda 72 

Iron  and  manganese   .         .         .  trace  trace 

Silica  separated  by  potash  .         .         12.23  9.39 

Silica  in  combination  with  alumina       20.46  20.34 

Alumina 35.01  25.59 

Water 12.12  8.94 


FELDSPAR. 

Under  the  general  name  feldspar,  have  been  confounded  a 
great  variety  of  minerals,  which,  while  differing  in  details,  agree 
in  general  conformation,  geological  situation,  and  to  a  certain 
extent  in  external  appearance.  They  are  found  universally  in 
granite,  trachyte,  porphyry,  and  other  plutonic  rocks,  as  a 
necessary  and  natural  ingredient.  They  are  also  found  in  veins 
or  masses  penetrating  or  imbedded  in  these  rocks. 

They  all  crystallize  in  the  oblique  rhombic  and  doubly  oblique 


CLAYS. 


471 


rhombic  (monoclinate  and  triclinate)  systems.  It  is  remarkable 
that  the  triclinate  feldspars  abound  in  soda  and  lime,  while  those 
of  the  monoclinate  system  contain  a  larger  quantity  of  potassa. 
The  feldspathic  minerals  are  also  analogous  in  their  chemical 
constitution,  all  of  them  being  double  silicates  of  alumina,  and 
some  alkali  or  alkaline  earth.  Their  lustre  is  either  pearly  or 
vitreous.  Their  color  varies,  being  red,  gray,  greenish,  flesh- 
colored,  roseate,  pure  white,  milky,  transparent,  or  translucent. 
They  lose  no  water  when  ignited ;  and,  at  a  high  heat,  are 
glazed  on  the  surface,  or  fused  to  a  transparent  glass  full  of 
bubbles.  Acids  do  not  attack  them ;  caustic  alkalies  affect  them 
but  slightly,  and  then  mainly  upon  the  surface,  when  the  action 
of  air  and  moisture  has  produced  incipient  decomposition. 

Analysis  has  shown  the  composition  of  the  great  majority  of 
feldspars  to  be  A]203,3Si03  +  Ko,Si03.  The  potash  is  often  re- 
placed, in  whole  or  in  part,  by  soda,  lime,  lithia,  or  magnesia, 
and  a  portion  of  the  alumina  by  sesquioxide  of  iron. 

Adularia  is  a  beautiful  transparent  variety  of  feldspar,  usually 
found  in  granite.  It  occurs  at  Haddam  and  Norwich,  Conn. ; 
Brimfield,  Mass. ;  and  Parsonsfield,  Me.  Its  composition,  ac- 
cording to  Berthier's  analysis,  is : — 

Silica 64.20 

Alumina 18.40 

Potassa  .......  16.95 

Loss .45 


100.00 


Crlassy  feldspar  is  usually  found  in  trachytic  rocks,  and  con- 
tains a  notable  proportion  of  soda,  as  may  be  seen  by  the  fol- 
lowing analysis  by  Berthier,  of  a  specimen  from  Mont  d'Or : — 

Silica  .......         66.1 


Alumina 

Potassa 

Soda 

Magnesia 

Loss 


19.8 
6.9 
3.7 
2.0 
1.5 


100.0 


472         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 


Common  feldspar  includes  a  number  of  subtranslucent  varieties. 
We  subjoin  two  analyses,  by  Booth  and  Boye  ;  the  first,  of  a 
massive,  highly  translucent  variety,  found  about  six  miles  north- 
west of  Wilmington,  in  Delaware ;  the  second,  of  a  bluish  and 
smoky  feldspar,  from  the  Brandywine  quarries  of  blue  rock,  a 
few  miles  north-east  of  Wilmington,  Delaware.  The  specific 
gravity  of  the  first  was  2.562  ;  of  the  second,  2.603: — 


Silica 

65.24 

66.51 

Alumina 

19.02 

17.67 

Potassa 

1L94 

9.81 

Soda 

3.06 

3.03 

Lime 

.33 

1.24 

Magnesia 

.13 

.30 

Oxide  of  iron,  &c.    . 

trace 

1.33 

Loss 

.28 

.11 

100.00 


100.00 


Jllhite  is  one  of  the  soda-feldspars.  It  is  whiter  and  more 
pearly  in  its  lustre  than  common  feldspars,  and  belongs  to  the 
triclinate  system  of  crystallization.  Sometimes,  but  rarely,  it 
is  pale  bluish,  greenish,  grayish,  or  reddish,  and  may  be  either 
transparent  or  opaque. 

It  often  replaces  feldspar  in  granite,  sienite,  &c.,  and  is  found 
in  Delaware,  associated  with  common  feldspar,  from  which  it  is 
distinguished  by  its  more  pearly  lustre.  It  resembles  feldspar  in 
its  chemical  reactions.  Its  specific  gravity  varies  from  2.6  to 
2.68.  We  subjoin  two  analyses  of  American  albite  by  Booth 
and  Boyd ;  the  first,  of  a  crystalline  and  granular  specimen, 
from  Chester  County,  Pennsylvania ;  the  second,  of  a  highly 
crystalline  piece,  from  the  vicinity  of  Wilmington,  Delaware : — 


Silica 

67.72 

65.46 

Alumina 

20.54 

20.74 

Peroxide  of  iron 

trace 

0.54 

Magnesia 

0.34 

0.74 

Lime 

0.78 

0.71 

Soda 

10.65 

9.98 

Potassa 

0.16 

1.80 

100.19 


99.97 


PORCELAIN.  473 

It  is  hardly  necessary  to  say  that  only  the  whitest  varieties 
of  this  mineral  can  be  used  in  the  manufacture  of  porcelain.  It 
is  employed  both  for  body  and  glaze. 

QUARTZ   SAND. 

Quartz  is  another  of  the  granitic  minerals,  and  has  of  course 
a  very  extensive  distribution  over  the  surface  of  the  earth. 

It  crystallizes  in  the  hexagonal  system,  usually  in  prisms, 
terminated  by  six-sided  pyramids.  It  is  also  found  granular 
and  compact,  rarely  fibrous.  When  perfectly  pure,  it  is  color- 
less or  white,  depending  upon  the  arrangement  of  its  particles. 
Its  lustre  is  vitreous,  rarely  resinous ;  and  its  fracture  usually 
conchoidal.  It  is  generally  contaminated  with  foreign  substances ; 
of  Avhich  alumina,  the  alkaline  earths,  and  the  metallic  oxides 
are  the  most  common.  The  latter  communicate  to  it  the  differ- 
ent colors  characteristic  of  its  varieties. 

Rock  crystal  is  the  purest  variety.  It  is  perfectly  colorless 
and  transparent,  hard,  and  infusible.  It  is  insoluble  in  every 
acid  but  the  hydrofluoric.  The  crystallized  variety  is  with  dif- 
ficulty attacked  by  caustic  potassa ;  the  amorphous  much  more 
easily.  When  used  in  the  manufacture  of  porcelain,  it  is  first 
heated  to  redness,  then  quenched  suddenly  in  water,  and  reduced 
to  a  fine  powder  by  levigation  with  water. 

These  are  the  materials  used  in  the  manufacture  of  the  body 
and  glaze  of  porcelain.  The  colors  are  given  to  it  by  the  metal- 
lic oxides,  which  will  be  described  after  we  shall  have  examined 
the  structure  of  porcelain. 


CHAPTER    VI. 

PORCELAIN. 

The  beautiful  white  ware  to  which  the  name  of  porcelain  has 
been  given,  was  unknown  to  those  nations  we  commonly  call  the 
ancients.     To  the  stationary  people  of  China,  however,  it  is  an 


474         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

old  article  of  manufacture,  having  been  made  in  that  remote 
empire  many  centuries  before  the  advent  of  Christ.  It  was  first 
introduced  into  Europe  by  the  Portuguese,  from  whose  language 
the  term  jJorcelain  is  derived.  This  term  porcellana  is  supposed 
to  have  been  originally  applied  to  the  porcelain-shell,  and  trans- 
ferred to  the  ware  on  account  of  its  resemblance  to  that  beauti- 
ful production  of  nature.  The  name  China,  by  which  this  fine 
pottery  is  still  known,  points  out  the  country  in  which  it  origi- 
nated, and  from  which  it  was  first  imported  by  the  occidental 
nations.  It  was  very  imperfectly  imitated  in  France  in  the 
seventeenth  century. 

The  first  European  manufacturer  of  porcelain  was  Botticher, 
a  German,  the  founder  of  the  famous  manufactory  of  Meissen. 
Addicted  to  alchemical  pursuits,  he  got  himself  into  trouble  with 
the  kings  of  Prussia  and  of  Poland,  who  attempted  to  force  out 
of  him  the  secret  of  gold-making,  which  he  professed  to  possess. 
At  last,  such  rigorous  measures  were  adopted  that  he  was  com- 
pelled to  confess  his  ignorance  of  the  philosopher's  stone,  but 
endeavored  to  appease  Augustus  II.,  of  Poland,  who  had  him 
in  prison,  by  assuring  that  monarch  that  he  was  acquainted  with 
the  art  of  porcelain  manufacture.  He  had,  indeed,  made  a  red 
stoneware  very  nearly  allied  to  porcelain,  and,  after  many  ex- 
periments, carried  on  in  his  prison,  he  succeeded,  in  1709,  in 
producing  the  true  white  porcelain.     He  died  in  1719. 

The  art  spread  slowly  from  Saxony.  In  1720,  it  "syas  intro- 
duced at  Vienna;  in  1751,  at  Berlin;  in  1755,  at  Nymphen- 
burg,  near  Munich;  in  1758,  at  St.  Petersburg;  and  in  1765, 
after  the  kaolin  of  St.  Yrieux  had  been  discovered,  it  superseded 
the  tender  porcelain  at  Sevres,  near  Paris. 

There  are  two  substances  which  have  received  the  name  of 
porcelain;  the  tender  porcelain,  or  iron-stone  China,  of  the 
French  and  English — which  is  only  a  vitreous  frit  containing 
substances  of  difficult  fusibility — and  the  hard  or  true  porcelain, 
consisting  of  burnt  clay  and  a  flux  of  quartzose  feldspar. 

English  tender  porcelain  approximates  much  more  nearly  to 
true  porcelain  than  the  French  ware.  It  is  made  of  plastic  clay ; 
kaolin  from  Cornwall;  Cornish  stone,  a  mixture  of  quartz,  kaolin, 
and  undecomposed  feldspar;  burnt  bones;  chalk  flints,  and  steatite. 


PORCELAIN.  475 

The  latter  substance  is  said  to  diminish  the  contraction  of  the 
wares  during  the  baking.  These  materials  are  ground  finely, 
elutriated,  and  mixed  with  a  frit  composed  of  Cornish  stone, 
flint,  soda,  borax,  and  oxide  of  tin.  The  ware  is  twice  fired, 
and  the  temperature  of  the  oven  is  regulated  by  small  trial 
pieces,  which  are  withdrawn  from  time  to  time.  The  glaze  re- 
sembles the  frit  in  its  composition,  with  the  addition  of  carbon- 
ate of  lime  and  some  lead. 

Recent  analyses  of  English  china  make  its  composition: 
silica,  40.60;  alumina,  24.15;  lime,  14.22;  protoxide  of  iron 
and  phosphate  of  lime,  15.82;  magnesia,  .43;  alkali  and 
loss,  4.78. 

The  true  porcelain  has  the  kaolin  for  its  basis,  which,  being 
a  plastic  clay,  is  easily  moulded  into  any  desired  form.  Kaolin 
alone,  however,  would  turn  to  a  porous,  opaque  body ;  a  flux  is 
therefore  introduced,  which  consists  of  feldspar,  chalk,  gypsum, 
broken  porcelain,  or  some  such  material.  This,  while  it  prevents 
the  kaolin  from  shrinking  out  of  shape,  assists  in  vitrifying  the 
mass. 

It  is  essential  to  the  beauty,  and,  indeed,  to  the  very  exist- 
ence of  good  porcelain,  that  these  difi"erent  ingredients  should 
be  reduced  to  the  finest  possible  state  of  division,  and  mixed  in 
the  most  intimate  manner.  For  this  purpose,  mills  are  used, 
and  the  ingredients  elutriated  separately,  and  mixed  while  they 
are  still  in  the  condition  of  a  soft,  thin  mud.  The  proportion 
found  at  Sevres  to  yield  the  best  results  is:  silica,  58;  alumina, 
34.5;  lime,  4.5;  potash,  3.  The  wet  pastes  are  mixed  in  this 
proportion  by  measurement,  the  weight  of  dry  matter  in  a 
given  bulk  of  mud  having  been  previously  ascertained.  It  must 
be  remarked,  however,  that  it  is  by  no  means  certain  that  such 
a  mixture  as  that  of  Sevres  will  always  yield  porcelain  of  the 
same  quality,  since  very  much  depends  on  the  manner  in  which 
the  proximate  elements  of  the  paste  are  combined. 

The  paste  thus  obtained  must  be  dried  to  a  mass  that  can  be 
easily  kneaded.  Numerous  difficulties  are  here  to  be  overcome. 
It  must  not  be  dried  too  fast,  or  it  will  lose  plasticity,  nor  can 
it  be  allowed  to  drain,  as  the  heavier  particles  will  sink  to  the 
bottom,  and  the  uniformity  of  the  mass  be  destroyed.     The  old 


476         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

method  of  overcoming  this  was  to  draw  off  the  mixture  into 
boxes  with  bottoms  of  plaster  of  Paris,  which  absorbed  the 
moisture.  Another  method,  which  has  superseded  the  last,  is 
to  subject  the  mud  to  strong  pressure;  while  another  very  ele- 
gant plan  has  been  suggested,  making  use  of  atmospheric  pres- 
sure. The  paste  is  thrown  on  thick  layers  of  felt,  resting  on 
metallic  sieves,  which  are  adapted  to  iron  funnels.  These  ter- 
minate in  an  iron  tube  communicating  with  a  close  chamber, 
from  which  the  air  can  be  easily  exhausted.  The  weight  of  the 
atmosphere  then  forces  the  fluid  through  the  pores  of  the  felt, 
and  a  rapid  filtration  is  accomplished. 

The  pliancy  of  the  mass  is  greatly  increased  by  the  process 
of  mouldering.  This  consists  in  beating  up  the  paste  in  small 
balls,  and  laying  them  aside  in  a  damp  place,  where  the  organic 
matter  they  contain  ferments.  A  fetid  smell  is  emitted,  the 
centre  of  the  lumps  become  black,  but  lose  that  color  as  the  air 
penetrates  them.  It  is  difficult  to  account  for  the  increased 
pliability  of  the  mass  in  consequence  of  this  process,  but  it  is  so 
well  understood  by  practical  men,  that  they  are  in  the  habit  of 
mixing  honey,  syrup,  and  other  organic  matters  with  their  clay, 
in  order  to  facilitate  the  change. 

The  paste  thus  prepared  is  moulded,  cast  or  carved  into  the 
desired  form,  and  the  different  articles  made  from  it  are  dried 
in  the  shade  till  they  cease  to  lose  weight.  They  are  then 
burned  slightly,  preparatory  to  putting  on  the  glaze.  The  ware 
after  this  first  firing  is  called  biscuit. 

The  glaze  of  porcelain  is  a  glass  entirely  free  from  lead.  In 
some  places,  it  is  composed  of  kaolin,  gypsum,  and  broken  por- 
celain, so  that  it  is  a  glass  containing  alumina  and  lime,  with 
the  small  quantity  of  potash  contained  in  the  old  porcelain.  At 
Sevres,  the  glaze  is  composed  of  the  pegmatite*  from  St.  Yrieux, 
and  consists,  therefore,  of  quartz  and  feldspar.  The  average  pro- 
portions of  Sevres  glaze  are  silica,  74 ;  alumina,  17,  and  potash, 
9,  with  a  little  lime  and  magnesia.  The  proper  fusibility  of  the 
glaze  is  an  exceedingly  important  point  to  arrive  at.  Should  it 
be  not  sufficiently  fusible,  it  will  not  form  an  even  surface,  but 
will  appear  wavy.     Should  it  be  too  fusible,  it  will  melt  before 

*  Graphic  granite. 


PORCELAIN.  477 

the  body  is  sufficiently  baked,  sink  into  the  porcelain,  and  leave 
the  surface  rough  and  dry.  To  insure  the  uniform  distribution 
of  the  glaze  over  the  surface  of  the  ware,  the  article  to  be 
glazed  is  dipped  into  a  tub  containing  the  materials  suspended 
in  water. 

Porcelain  is  milk-white,  without  any  tinge  of  blue.  Its  value 
depends  upon  the  closeness  of  its  texture  and  the  intimacy  with 
which  its  hard  glaze  is  connected  with  the  body.  The  manner 
in  which  its  two  component  parts,  the  kaolin  and  the  flux,  are 
connected  with  one  another  has  been  variously  explained.  It 
was  formerly  supposed  that  the  kaolin  remained  a  sort  of  infu- 
sible skeleton,  through  which  molten  feldspar  or  other  flux  was 
poured,  giving  translucency  to  the  mass,  as  opaque  paper  is 
rendered  transparent  by  being  saturated  with  varnish.  Accord- 
ing to  the  recent  microscopic  observations  of  Oschatz  and 
Wachter,  however,  the  porcelain  mass  consists  of  a  vitreous 
matrix,  intersected  in  all  directions  by  minute  needle-shaped 
crystals  ;  the  want  of  transparency  being  due  to  the  reflection 
and  refraction  of  light  among  these  minute  crystalline  particles. 

Porcelain  undergoes  a  notable  diminution  of  volume  during 
the  process  of  baking.  The  slightest  variation  in  the  component 
parts  of  a  paste  will  alter  this  shrinking,  but  in  the  same  paste 
the  contraction  is  constant,  so  that  it  can  be  estimated  with 
great  accuracy.  The  average  linear  contraction  is  13  per  cent, ; 
this  may,  however,  fall  to  7  or  rise  to  17  per  cent.  The  average 
contraction  in  volume  is  stated  at  39  per  cent. 

The  density  is  increased  with  the  contraction.  The  specific 
gravity  of  the  dry  mass,  once  heated,  is  2.305  ;  after  thorough 
baking,  it  is  2.478.  This  is  taken  from  the  mass,  and  therefore 
includes  the  pores.  It  is  remarkable,  however,  that,  when  re- 
duced to  powder,  its  specific  gravity  diminishes  with  the  increase 
of  temperature  to  which  it  has  been  subjected.  Thus,  according 
to  Malaguti,  the  powder  of  once  heated  porcelain  had  a  specific 
gravity  of  2.619  ;  of  half-baked,  2.44  ;  thoroughly  baked,  2.242. 
It  has  been  supposed,  in  order  to  account  for  this  phenomenon, 
that  while  the  particles  themselves  are  expanded,  they  are 
brought  in  closer  proximity  to  each  other,  and  thus,  while  the 
specific  gravity  of  individual  particles  is  diminished,  that  of  the 
mass  is  increased. 


478         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

A  number  of  analyses  of  porcelain  have  been  published.  We 
select  three  ;  the  first,  of  Sevres  porcelain,  by  Laurent  and  Ma- 
laguti ;  the  second,  of  Berlin  ware,  by  Cowper  ;  and  the  third,  of 
Chinese,  by  the  same  chemist. 


1. 

2. 

3. 

Silica            ....         58.0 

72.96 

71.04 

Alumina,  with  a  little  protoxide 

of  iron           .         .         .         34.5 

24.78 

22.46 

Lime 4.5 

1.04 

3.82 

Alkali          ....          3.0 

1.22 

2.68 

100.0      100.00      100.00 


CHAPTER    VII. 

COLORING  MATERIALS. 

The  art  of  tinting  porcelain  depends  upon  a  knowledge  of  the 
management  of  the  vitrifiable  pigments.  Like  all  other  pigments, 
they  may  be  mixed  so  as  to  produce  a  very  great  variety  of  tone  and 
tint,  but,  unlike  common  coloring  matters,  chemical  changes  and 
reactions  take  place  among  them  at  the  high  heat  to  which  they 
are  necessarily  exposed,  so  that  the  artist  must  take  into  ac- 
count not  only  the  efi"ects  of  the  blending  of  colors,  but  also 
the  chemical  modifications  of  the  components  of  his  palette. 

The  number  of  colors  used  by  the  manufacturer  of  porcelain 
teeth  is  not  large.  He  has  not  those  varied  and  brilliant  tints 
to  apply  which  the  artist  at  Sevres  or  Meissen  requires  for  the 
production  of  his  beautiful  pictures.  His  tints  are  few  and  un- 
decided; but  the  very  vagueness,  delicacy,  and  indistinctness  of 
them,  demand  close  attention,  and  no  little  knowledge  of  the 
subject.  These  colors  are  various  shades  of  gray,  yellow,  and 
rose,  obtained  sometimes  directly,  sometimes  by  the  blending  of  , 
more  positive  tints. 

The  principal  oxides  and  metals  used  and  the  colors  they  pro- 
duce are  given  on  the  next  page. 


COLORING  MATTERS. 


479 


Metals  and  Oxides. 
Platina  sponge  or  black,  . 
Platino-chloride  of  ammonium, 
Gold,  in  a  state  of  minute  division, 
Peroxide  of  gold, 
Purple  of  Cassius, 
Oxide  of  titanium. 
Oxide  of  uranium, 
Oxide  of  zinc. 
Oxide  of  silver, 
Oxide  of  cobalt. 
Oxide  of  manganese. 


Colors  produced. 
Grayish-blue. 
Blue. 
Rose  red. 
Bright  rose  red. 
Purplish  rose  color. 
Bright  yellow. 
Greenish  or  orange  yellow. 
Lemon  yellow. 

Brilliant  blue. 
Purple. 


In  the  above  table,  the  metals  and  oxides  are  regarded  as 
perfectly  pure.  Any  deviation  from  absolute  purity  will  of 
course  modify  the  tint.  Thus  the  oxide  of  titanium  commonly 
used  is  not  pure,  but  contains  iron.  The  consequence  is  that 
the  bright  yellow  tint  of  the  pure  oxide  is  not  obtained,  but  a 
dingy  tint  far  better  suited  to  the  purpose  of  the  manufacturer, 
who  desires  to  imitate  the  dusky  yellowish  color  of  many  teeth. 
Desirabode's  tints  differed  somewhat  from  these,  and  most  of 
them  are  now  generally  abandoned.  He  obtained  his  blue  from 
cobalt,  his  gray  from  platina  and  mercury,  his  violet  and  red 
from  gold,  his  bluish-gray  from  bismuth,  his  pale  yellow  from 
silver,  his  brownish-yellow  from  iron,  his  purple  gray  from  man- 
ganese, his  straw  yello\^  from  uranium  and  titanium,  and  his 
pure  yellow  from  antimony.  Of  course,  he  blended  these  posi- 
tive colors  so  as  to  get  a  subdued  tint. 

In  the  preparation  of  the  above  colors,  much  care  and  no 
little  chemical  knowledge  are  required  to  get  accurate  results. 
Many  of  them  demand  a  very  complete  acquaintance  with  the 
reactions  of  the  metals  and  the  chemical  modes  of  separating 
them.  To  get  many  of  them  in  a  state  of  purity,  a  careful 
analysis  of  the  ores  of  the  metal  sought  for  is  required,  and 
then  great  skill  and  delicacy  are  necessary  in  the  manipulations. 
Unless,  therefore,  a  manufacturer  possesses  the  necessary  know- 
ledge, it  is  much  better  that  he  should  purchase  his  oxides 
from  a  competent  chemist  than  trust  to  the  chances  of  his  own 


480         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

success.  The  following  directions,  however,  will  assist  those 
who  desire  to  get  a  personal  experience  in  these  manipulations. 

Platina  sponge  and  platino-chloride  of  ammonium  have 
already  been  described. 

Gold,  in  q  minute  state  of  division,  is  obtained,  as  already 
directed,  by  precipitating  the  chloride  with  protosulphate  of 
iron,  and  washing  the  blackish  powder,  first  with  hydrochloric 
acid  and  then  with  distilled  water.  It  is  also  prepared  by 
grinding  filings  or  foil  with  a  little  spar  on  a  mortar  or  a  marble 
slab.  Another  process  is  to  melt  in  a  crucible  with  borax  12 
parts  of  pure  silver,  4  of  gold,  and  1  of  tin.  The  alloy  is  either 
granulated  or  rolled  out  in  foil,  and  then  treated  with  nitric 
acid,  till  all  the  silver  is  taken  up.  The  residual  gold  is  then 
thoroughly  washed. 

This  process  does  not  give  pure  metallic  gold.  There  will 
always  be  a  little  silver  and  a  notable  quantity  of  oxide  of  tin 
mixed  up  with  it. 

Another  very  convenient  way  of  obtaining  finely  divided 
gold  is  to  throw  it  down  from  the  chloride  with  oxalic  acid. 
The  best  process  is  that  with  protosulphate  of  iron,  if  due  care 
is  taken  to  free  the  solution  of  the  chloride  from  nitric  acid 
before  precipitating,  and  if  the  iron  be  thoroughly  washed  out 
of  the  precipitated  gold. 

The  peroxide  of  gold  is  best  made  as  already  described.  The 
more  common  method  is  to  precipitate  the  gold  with  ammonia. 
The  yellow  precipitate  obtained  in  this  way,  however,  is  not  an 
oxide  but  a  mixture  of  the  oxide  with  ammonia  and  chlorine. 

The  purpile  of  Cassius  has  already  been  described. 

TITANIC  ACID,  TiOg. — OXIDE  OF  TITANIUM. 

This  is  found  native  in  various  degrees  of  purity.  Its  prin- 
cipal ores  are  spliene,  rutile,  titaniferous  iron,  anatase,  and 
brookite. 

Sphene,  called  also  titanite  and  menachan  ore,  is  a  silico- 
calcareous  oxide  of  titanium,  or  a  silicate  and  titanate  of  lime. 
Rose's  formula  for  it  is  3CaO,Si03  +  2Ti02,Si03;  Berzelius's 
2(CaO,Si03)+CaO,3Ti02.     It  crystallizes  in  oblique  rhombic 


'       COLORING  MATTERS.  481 

system.  Its  colors  are  various  shades  of  yellow,  green,  brown, 
gray,  and  black ;  its  lustre  is  adamantine  resinous.  It  is  brittle, 
and  either  transparent  or  opaque.  Its  streak  is  white.  Before 
the  blowpipe,  it  fuses  on  the  edges,  with  some  puffing,  to  a  dark 
glass,  dissolves  in  borax  with  a  yellow  color,  with  difficulty  in 
microcosmic  salt.  Tin  reduces  it,  giving  first  a  yellow  and 
then  a  violet  tint  to  the  bead.  It  occurs  in  primary  rocks 
in  many  places,  but  rarely  in  masses. 

Rutile  crystallizes  in  prisms  terminated  by  octahedra,  and 
often  twinned  by  turning  180°  on  an  octahedral  plane.  Its  colors 
vary  from  brownish-red  to  dark  brown  ;  its  lustre  is  metallic  or 
adamantine ;  it  is  subtransparent  or  opaque  ;  its  fracture  is 
subconchoidal  and  uneven,  and  its  streak  light  brown. 

By  itself,  it  is  infusible,  but  with  borax  it  gives  in  the  outer 
flame  a  greenish,  in  the  inner  a  violet  glass.  In  the  inner  flame, 
with  microcosmic  salt,  it  gives  a  red  glass,  and  sometimes,  with 
the  addition  of  tin,  a  blue  or  violet  one.  It  fuses  with  soda, 
with  efi"ervescence,  to  a  bead  which  sometimes  shows  manganese. 
When  treated  with  soda,  it  usually  shows  tin.  It  is  titanic  acid, 
combined  with  more  or  less  oxide  of  iron. 

It  occurs  in  primary  rocks  and  in  older  limestones.  In  Lan- 
caster County,  Pennsylvania,  very  large  crystals  are  found. 

Anatase,  octahedrite,  oisanite,  or  pyramidal  titanium  ore, 
occurs  in  small  octahedral  crystals  belonging  to  the  tetragonal 
system.  Its  color  is  blue,  passing  into  brown,  red,  black,  and 
greenish-yellow,  by  transmitted  light ;  its  lustre  is  splendent  and 
submetallic;  its  streak,  grayish-white.  It  is  either  translucent  or 
opaque.  Heat  makes  it  phosphoresce,  for  a  moment,  with  a 
reddish-yellow  light.  Its  blowpipe  reactions  are  those  of  pure 
titanic  oxide. 

Brookite  crystallizes  in  right  rhombic  prisms.  Its  color  is 
hair-brown,  passing  into  orange  ;  its  lustre,  brilliant  metallic 
adamantine  ;  its  streak  pale  yellowish.  It  is  brittle,  and  either 
translucent  or  opaque.  It  is  found  at  Phoenixville,  near  Phila- 
delphia. 

Titaniferous  or  titanic  iron  (Iserine,  Menakan,  &c.)  crystal- 
lizes in  rhombs  with  large  end  planes  belonging  to  the  hexagonal 
system  ;  but  is  usually  found  in  plates  or  grains.     It  is  more  or 
31 


482         MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

less  magnetic,  opaque,  iron  black,  with  a  submetallic  lustre  and 
a  conchoidal  fracture.  It  is  infusible  by  itself,  and  gives  reac- 
tions of  both  iron  and  manganese  with  the  fluxes.  With  micro- 
cosmic  salt,  in  the  inner  flame,  it  gives  a  reddish  glass,  which 
tin  either  decolorizes  or  renders  violet.  Aqua  regia  takes  up 
the  iron  and  leaves  titanic  acid.  It  is  usually  supposed  to  be 
a  mixture  of  titanate  of  iron  with  variable  quantities  of  the 
oxide  and  sesquioxide  of  that  metal.  Rose  and  Scherer,  how- 
ever, believe  it  to  be  a  mixture  of  the  sesquioxides  of  titanium 
and  iron. 

Pure  titanic  acid  is  usually  obtained  from  rutile  or  titanic  iron. 
The  ore  is  reduced  to  fine  powder,  and  its  iron  oxides  extracted 
with  hydrochloric  acid.  The  residue  is  then  fused  with  carbo- 
nate of  soda,  and  the  resulting  mass  treated  with  water  to  dis- 
solve excess  of  alkali.  Acid  titanate  of  soda  remains,  which  is 
washed  in  a  filter,  until  the  liquid  passes  through  cloudy.  It  is 
then  removed  from  |the  filter,  and  dissolved  in  strong  hydro- 
chloric acid.  The  solution  is  diluted  with  water,  charged  with 
sulphuretted  hydrogen,  which  throws  down  whatever  tin  may  be 
contained  in  the  mineral.  This  is  separated  by  filtration,  and 
the  liquid  poured  in  a  flask,  which  is  corked,  after  the  addition 
of  ammonia.  A  precipitate,  consisting  of  titanic  acid  and  the 
sulphurets  of  iron  and  manganese  now  falls.  The  sulphurets 
are  separated  from  the  acid  by  the  addition  of  sulphurous  acid, 
in  excess,  and  the  titanic  acid  which  remains  is  thoroughly 
washed. 

A  simpler  method  of  obtaining  it  is  to  ignite  titanic  iron 
with  sulphur,  so  as  to  convert  the  iron  into  a  sulphuret.  The 
sulphuret  of  iron  is  removed  by  hydrochloric  acid.  By  repeat- 
ing the  operation  several  times,  the  titanic  acid  may  be  obtained 
quite  free  from  iron. 

Titanic  acid  is  a  white,  tasteless,  infusible  powder,  which 
becomes  yellow  on  the  application  of  heat,  but,  like  oxide  of 
zinc,  regains  its  whiteness  as  it  cools.  Like  silicic  acid,  it  occurs 
in  two  modifications,  a  soluble  and  an  insoluble.  Like  it,  too, 
the  former  is  converted  into  the  latter  by  ignition. 

Ammonia  precipitates  it  white,  gelatinous,  soluble  in  acids, 
and  to  some  extent  in  carbonated  alkalies.     Ferrocyanide  of 


COLOKINa  MATTERS.  483 

potassium  throws  down  a  reddish-brown  precipitate,  soluble  in 
excess  of  the  reagent ;  zinc,  iron,  and  tin,  added  to  its  solutions, 
first  change  their  color  to  a  blue  or  purple  hue,  and  then  throw 
down  a  precipitate  of  the  same  tint,  which  gradually  changes  to 
titanic  acid.  This  precipitate  is  supposed  to  be  a  sesquioxide 
of  titanium. 

For  the  purposes  of  the  dentist,  the  purer  varieties  of  the 
native  acid  are  selected,  and  reduced  to  fine  powder.  As  already 
stated,  the  presence  of  a  small  quantity  of  iron  or  manganese  is 
not  objectionable,  as  the  tint  is  lowered  by  them,  so  as  to  ap- 
proximate more  nearly  to  the  natural  hue  of  the  teeth.  It  is 
necessary,  however,  for  the  operator  to  know  either  the  exact 
proportion  of  these  metals  present,  or  the  precise  color  which 
any  given  specimen  of  titanium  will  yield.  Trial  pieces  should, 
therefore,  always  be  used,  or  the  pure  acid  employed  and  the 
color  deadened  by  other  oxides. 

OXIDE    OF    URANIUM. 

Uranium  was  originally  discovered  by  Klaproth  in  1788,  as 
an  oxide,  but  Peligot  was  the  first  to  obtain  the  metal,  in  1841. 

It  is  contained  in  considerable  quantity  in  uranite,  of  which 
there  are  two  varieties,  both  represented  by  the  formula  oRO 
P0^4-2(3U203,P05)  +  24HO.  In  one  of  these,  lime  uranite,  the 
RO  is  CAO  with  a  little  BaO.  In  the  other,  chalcolite  or  cop- 
per uranite,  it  is  CuO.  Both  varieties  crystallize  in  the  quad- 
ratic system,  with  many  octahedra.  The  lustre  of  the  end- 
plane  is  pearly,  of  the  rest  adamantine.  Both  are  transparent 
or  subtranslucent,  sectile,  and  brittle.  The  color  of  lime  uranite 
is  yellow  or  greenish,  that  of  copper  uranite  emerald  and  other 
bright  greens  with  a  paler  streak.  Both  yield  water  when  heated 
in  a  tube,  becoming  yellow  as  it  is  expelled.  Both  fuse  on  coal 
with  effervescence  to  a  black  bead  with  a  crystalline  surface  ; 
dissolve  in  fluxes  with  a  yellow  color  in  the  outer  and  a  green  in 
the  inner  flame,  and  form  a  yellow  slag  with  soda.  Chalcolite 
gives,  besides  these,  the  reactions  of  copper. 

Uranium,  or  pitchblende,  contains  a  still  larger  proportion  of 
this  metal.  It  occurs  massive,  is  opaque,  black,  brownish  or 
grayish  in  color,  with  a  dull,  submetallic  lustre  and  a  conchoidal 


484       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

fracture.  It  is  infusible  alone,  but  with  the  fluxes  it  dissolves 
into  a  yellow  glass  in  the  outer  and  a  green  one  in  the  inner  flame. 
By  the  aid  of  heat,  it  dissolves  in  both  nitric  and  nitro-muriatic 
acids. 

It  is  found  in  many  places  in  Europe.  In  the  United  States 
it  has  been  found  at  Middletown,  Connecticut ;  Chesterfield, 
Massachusetts ;  and  Chester,  Pennsylvania,  on  the  Delaware 
River. 

Uranium  has  three  oxides.  The  first  (UO)  is  a  reddish-brown 
or  iron  gray  powder.     It  forms  green  salts. 

The  second,  or  common  oxide  of  uranium,  is  a  mixture  of  the 
first  and  third,  and  is  obtained  in  large  quantities  from  uranium 
or  pitchblende,  which  contains  from  50  to  90 g  of  it.  The  ore 
is  dissolved  in  aqua  regia,  and  charged  with  sulphuretted  hydro- 
gen, to  remove  other  metals,  and  the  solution  filtered  clear  from 
the  precipitate.  The  filtrate  is  heated  with  nitric  acid  to  perox- 
idize  the  iron  and  uranium,  which  are  then  thrown  down  by  am- 
monia. The  precipitate  is  washed,  and  then  treated  with  car- 
bonate of  ammonia,  which  dissolves  the  cobalt,  zinc,  nickel,  and 
uranium.  The  ammonia  is  volatilized  by  heat,  and  the  residue 
washed,  dried,  and  ignited.  Digestion  with  muriatic  acid  takes 
up  the  other  oxides,  and  leaves  the  green  oxide  of  uranium. 

It  is  a  dark  green  or  black  powder,  soluble  in  concentrated 
hydrochloric  or  nitric  acid,  when  digested  with  either  in  a  close 
vessel ;  peroxidized  by  nitric  acid,  forming  green  salts  with  the 
acids,  which  dissolve  it  unchanged. 

The  sesquioxide,  UgOj,  is  obtained  by  dissolving  the  green 
oxide  in  nitric  acid,  evaporating  to  dryness,  and  fusing  it  at  a  low 
heat  to  drive  oS  nitric  acid.  It  is  then  digested  in  boiling  water 
as  long  as  anything  soluble  is  taken  up,  and  the  pure  oxide  re- 
mains as  a  gold  or  orange  yellow  powder,  becoming  brick  red, 
from  loss  of  water,  by  careful  heating ;  and,  at  a  higher  tempe- 
rature, losing  oxygen  also.  Its  salts  are  yellow.  This  is  the 
oxide  used  by  the  manufacturer  of  porcelain  teeth. 


COLORINa  MATTERS.  485 


OXIDE    OF    MANGANESE. 

The  oxide  of  manganese  occurs  native  in  a  variety  of  forms. 
It  is  sometimes  mixed  with  lime,  as  in  manganese  spar,  and  man- 
ganocalcite,  sometimes  with  silica,  as  in  Fowlerite,  Troostite,  &c. 
Most  commonly,  however,  it  is  found  alone  or  only  contami- 
nated with  iron  and  other  accidental  admixtures.  3Ianganite 
is  a  crystallized  form,  containing  one  atom  of  water,  in  right 
rhombic,  longitudinally  striated  prisms.  It  is  most  frequently 
met  with,  however,  in  black,  earthy  masses,  which  are  always 
more  or  less  impure. 

There  are  no  less  than  six  different  degrees  of  oxidation  of 
this  metal,  the  protoxide,  MnO ;  the  red  oxide,  MngO^,  thought 
by  some  to  be  a  mixture  of  the  proto-  and  sesquioxides  ;  the 
black  or  sesquioxide,  MngOj ;  the  binoxide,  Mn02  >  manganic 
acid,  Mn03,  and  permanganic  acid,  MngO^.  Of  these,  the  third 
and  fourth  only  are  used  in  tinting  glass  and  porcelain. 

There  are  various  modes  of  obtaining  the  pure  oxides  from 
the  commercial  black  oxides.  One  of  the  simplest  and  readiest 
of  these,  is  to  make  an  intimate  mixture  of  the  peroxide  of 
commerce  with  half  its  weight  of  sal  ammoniac,  and  to  project  it 
portionwise  into  a  crucible  kept  constantly  at  a  red  heat.  The 
chlorine  of  the  salt,  in  this  process,  unites  with  the  oxide  of 
manganese,  to  the  exclusion  of  every  other  substance,  provided 
an  excess  of  that  oxide  be  present.  The  chloride  of  manganese 
is  extracted  from  the  mass  by  digestion  in  water.  Another  sim- 
ple method  is  to  mix  the  commercial  oxide  with  sulphuric  acid, 
to  a  paste,  to  introduce  this  into  a  crucible,  heat  it  to  redness 
for  half  an  hour  or  an  hour,  and  lixiviate.  In  either  case, 
the  sulphate  or  chloride  is  to  be  precipitated  by  an  alkaline 
carbonate  or  a  pure  alkali,  and  then  again  heated  to  redness. 
Should  the  peroxide  be  required,  the  last-mentioned  precipitate 
is  to  be  dissolved  in  nitric  acid,  and  the  resulting  nitrate  de- 
composed by  heating  it  to  a  commencing  redness. 

Oxide  of  zinc  is  obtained  by  simply  burning  the  metal  and 
collecting  the  fumes  as  they  rise. 

Oxide  of  silver  has  been  described  already. 


486       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 


OXIDE    OF    COBALT. 

The  ores  of  cobalt  almost  always  contain  nickel,  iron,  arsenic, 
and  manganese.  A  variety  of  processes  have  been  adopted  for 
the  separation  of  the  pure  oxide  on  the  great  scale.  We  shall 
only  specify  one  method,  that  of  Quesneville,  by  ■which  a  tolera- 
bly pure  oxide  can  be  obtained  from  the  ore. 

The  ore  is  to  be  boiled  in  nitric  acid,  to  convert  the  arsenic 
into  an  oxide,  which  combines  with  the  different  metals  pre- 
sent. The  solution  is  then  largely  diluted  and  filtered,  and  the 
arseniates  are  precipitated,  one  after  another,  by  means  of  car- 
bonate of  soda.  The  arseniate  of  cobalt,  which  is  the  most  solu- 
ble, precipitates  last.  The  alkali  is  to  be  added  in  small  quantities 
and  at  considerable  intervals  of  time,  the  solution  being  fre- 
quently stirred,  or  otherwise  agitated,  and  the  precipitates 
obtained,  after  each  addition  of  the  alkali,  being  allowed  to  sub- 
side thoroughly  from  the  clear  solution.  In  this  manner,  the 
colors  of  the  precipitates  can  be  distinctly  recognized.  When 
a  rose-colored  precipitate  begins  to  fall,  no  more  alkali  must  be 
added,  as  this  is  an  indication  that  cobalt  is  coming  down.  The 
solution  is  now  filtered  off  from  the  precipitates,  and  the  clear 
liquid  precipitated  by  a  saturated  solution  of  binoxalate  of  po- 
tassa,  which  in  a  few  hours  throws  down  the  cobalt,  mixed  with 
a  little  nickel.  The  latter  oxide  may  be  entirely  separated  from 
the  cobalt,  if  desired,  by  bringing  both  of  them  to  the  condition 
of  oxalates,  dissolving  the  mixed  salts  in  ammonia,  and  exposing 
to  the  air  for  several  days,  when  the  nickel  falls,  leaving  cobalt 
in  solution. 

A  preparation,  called  ashes  of  cobalt,  said  to  be  superior  to 
the  pure  oxide  as  a  coloring  material  for  teeth,  is  made  by  wrap- 
ping the  oxide  in  blue  English  laid  paper,  and  burning  it  in  a 
closed  crucible. 

In  the  production  of  the  natural  tints  of  the  teeth  and  gums 
from  these  positive  colors,  much  taste  and  skill  are  required.  No 
general  directions  can  be  given  which  will  meet  the  emergencies 


INCORRUPTIBLE  TEETH.  487 

of  particular  cases,  for  the  tints  of  natural  teeth  are  so  varied, 
that  the  variations  of  the  coloring  matters  to  imitate  them  must 
be  almost  endless.  The  quantity  of  oxide  introduced  into  the 
composition  must  be  extremely  small. 

Linderer  gives  receipts  for  five  different  shades  of  yellow  and 
of  blue,  and  for  six  of  the  greenish  tints.  To  37  pennyweights 
of  the  dry  materials  of  the  teeth,  he  adds  2  grains  of  titanic 
acid  for  his  palest  and  8  for  his  deepest  yellow  ;  and  Ih  grains 
of  platina  sponge  for  his  palest  and  4  for  his  deepest  blue.  For 
his  green  tints,  he  mixes  for  No.  1,  the  palest,  3  grains  of  titanic 
acid  with  1  of  platina  sponge,  and  for  No.  6,  the  deepest,  8 
grains  of  the  former  with  4  of  the  latter.  These  tints  are  for 
the  bodies. 

We  shall  return  to  this  subject,  after  having  described  the 
method  of  manufacturing  the  porcelain  teeth  themselves. 


CHAPTER    VIII. 

INCORRUPTIBLE   TEETH. 
HISTORY. 

Numerous  were  the  substitutes  employed  by  the  old  dentists 
to  replace  teeth  which  had  been  unfortunately  lost  or  removed 
from  the  mouth.  Human  teeth,  the  ivory  of  the  elephant  or 
hippopotamus,  and  such  animal  substances  constituted  their  sole 
resources.  These  were  objectionable  not  only  on  account  of  the 
imperfect  manner  in  which  they  imitated  the  natural  organs, 
but  also  by  reason  of  their  permeability  to  offensive  fluids,  the 
readiness  with  which  they  absorbed,  and  the  tenacity  with  which 
they  retained  disagreeable  eflSiuvia. 

It  was  to  the  discomfort  of  an  apothecary  of  St.  Germain, 
named  Duchateau,  that  the  world  owes  the  beautiful  and 
unchangeable  material  which  is  at  present  used  in  the  fabrication 
of  dental  substitutes.     This  vender  of  drugs,  having  had  the 


488       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

misfortune  to  lose  his  teeth,  had  supplied  the  deficiency  with  one 
of  the  ivory  imitations  common  in  his  day.  Living,  as  he  did, 
in  an  atmosphere  perpetually  tainted  with  the  various  disagreeable 
odors  arising  from  his  wares,  he  found  that  the  porous  animal 
substances  of  which  his  artificial  teeth  were  composed,  imbibed 
these  effluvia,  and  became  a  perpetual  source  of  discomfort  to 
their  wearer.  Casting  about  in  his  own  mind  for  a  substitute 
for  these  uncleanly  organs,  he  hit  upon  porcelain,  which  recom- 
mended itself  strongly  to  him  by  its  beauty,  impermeability, 
and  durability.  M.  Guerard  undertook  the  manufacture  of  the 
articles,  and  the  first  set  of  porcelain  teeth  saw  the  light  in 
Paris,  in  1776,  a  year  famed  for  a  more  memorable  revolution. 

Encouraged  by  his  success,  he  prevailed  on  others  who  were 
in  the  same  unpleasant  predicament  with  himself  to  resort  to  the 
same  expedient  for  relief.  He  had  several  complete  dentures 
made  for  difl'erent  distinguished  personages,  but  he  failed  for 
want  of  knowledge  of  the  practical  duties  of  the  dentist,  and 
for  some  time  these  substitutes  were  abandoned. 

After  a  time,  one  Dubois  Chement  (in  1788)  purchased  the 
right  of  Duchateau,  and  made  great  efi'orts  to  establish  these 
substitutes  in  the  confidence  of  the  public.  He  succeeded  in 
attracting  the  attention  of  the  French  Academy,  who  appointed 
a  committee  to  examine  his  process.  It  was  found  to  be  defective 
in  many  respects,  and  Dubois-Foucou,  who  was  one  of  the  com- 
mittee, set  to  work  to  improve  it.  At  last  he  succeeded  in 
getting  out  a  material  which,  with  some  modifications,  serves  as 
the  basis  of  our  present  processes. 

It  is  not  necessary  to  trace  our  history  farther.  Suffice  it  to 
say,  that  his  process  has  been  greatly  improved  since  those  days, 
and  that  our  own  country  has  not  been  behind  others  in  its  con- 
tributions to  the  advancement  of  this  beautiful  art. 

PREPARATION    OF   MATERIALS. 

In  all  operations  in  which  a  perfect  fusion  is  required,  it  is 
essential  that  the  substances  to  be  fused  should  be  reduced  to 
a  state  of  the  completest  possible  comminution,  and  mixed  in 
the  most  intimate  possible  manner.      The  semivitrification  of 


INCORRUPTIBLE  TEETH.  489 

porcelain  needs  the  same  fine  pulverization  and  perfect  admix- 
ture, for  it  is  a  true  fusion. 

Great  care  is  therefore  taken  to  comminute  the  materials  as 
completely  as  possible.  The  silex  is  first  heated  to  redness,  and 
then  suddenly  quenched  in  water.  This  makes  it  friable,  and 
very  much  facilitates  its  subsequent  reduction.  Some  prefer 
to  grind  up  the  coloring  matter  along  with  the  silex.  The 
grinding  is  usually  accomplished  in  porcelain  or  wedgewood 
mortars,  and  the  mass  is  commonly  kept  constantly  moist.  This 
answers  two  good  purposes  :  it  prevents  the  fine  particles  from 
rising  in  the  air,  and  it  facilitates  the  comminution  of  the  sub- 
stances. The  spar  is  treated  in  the  same  manner,  or  it  may  be 
powdered  without  any  preparatory  ignition.  The  kaolin  is 
directly  powdered. 

It  is  sometimes  necessary  to  purify  this  latter  ingredient,  as 
few  specimens,  however  fine,  are  totally  free  from  iron.  All 
that  is  necessary  is  to  digest  it  with  dilute  hydrochloric  acid, 
and  afterwards  to  wash  it  thoroughly.  Iron  is  injurious  to  the 
porcelain  in  more  ways  than  one.  It  not  only  gives  an  unplea- 
sant yellow  opacity  to  the  wares,  but  it  also  so  increases  the 
fusibility  of  the  compound  as  to  render  it  impossible  to  calculate 
upon  its  fusing  point. 

It  is  customary  with  some  manufacturers  to  reduce  their  silex 
to  a  much  finer  powder  than  their  spar.  They  think  that  they 
thereby  increase  its  transparency.  Some  go  so  far  as  to  make 
this  powder  very  coarse,  but  we  doubt  the  propriety  of  such  a 
mode  of  procedure.  It  is  the  fusible  portion  which  they  treat 
in  this  manner,  and  the  only  eff"ect  it  can  have  is  to  retard  the 
melting  of  the  spar.  Were  the  silex  left  coarse,  or  were  a  few 
fragments  additional  of  this  substance,  or  of  asbestos,  introduced 
into  the  body,  it  would,  like  the  cement  in  a  crucible,  materially 
diminish  contraction. 

The  extreme  comminution,  perfect  intermixture,  and  absolute 
purity  of  the  materials,  is  especially  to  be  insisted  on  in  the 
preparation  of  the  enamel.  Any  defect  becomes  very  manifest. 
Grains  of  unfused  silex  roughen  the  surface,  which  ought  to  be 
perfectly  smooth,  or  spots  and  stains  disfigure  it.  The  process 
of  grinding  the  substances  thoroughly,  then  stirring  them  with 


490       MATERIALS  USED  IN  MAKING  INCOKRUPTIBLE  TEETH. 

a  large  quantity  of  water,  allowing  the  coarser  particles  to  sub- 
side, and  decanting  the  finer  powder,  may  be  resorted  to  with 
advantage.  Audibran  used  a  porphyry  slab  and  muller  for 
levigating  the  materials  he  designed  to  use.  When  the  materials 
are  ground  under  water,  they  may  be  rapidly  dried  by  throwing 
the  paste  upon  some  clean  porous  substance,  such  as  a  well-dried 
slab  of  plaster  of  Paris,  till  so  much  water  is  abstracted  from 
it  as  to  leave  it  of  the  consistence  of  stiif  dough. 

Several  little  circumstances  must  be  attended  to  by  the  manu- 
facturer Avho  would  obtain  perfect  teeth.  Many  of  these  can 
only  be  learned  by  experience,  so  that  it  is  impossible  to  give 
general  directions  which  shall  apply  to  individual  cases.  A  few 
general  principles,  however,  may  be  stated,  which  will  serve  as 
a  guide  to  the  operator.  The  practical  details  must  in  this,  as 
in  all  other  cases,  be  determined  by  the  skill  and  tact  of  the 
manipulator.  It  is  necessary,  in  the  first  place,  to  use  pure 
water,  rain  water  is  best,  so  as  to  avoid  contaminations  of 
coloring  matters  and  of  salts,  the  latter  of  which  will  increase 
the  fusibility  of  the  pastes.  It  is  proper,  also,  to  let  the  kaolin 
moulder,  as  we  have  already  described  under  the  head  of 
porcelain.  The  contraction  in  the  furnace  to  which  we  have 
already  alluded  in  a  previous  chapter,  must  also  be  borne  in 
mind.  Audibran  recommends  to  make  all  the  teeth  and  blocks 
one-third  larger  than  they  are  designed  to  be  after  baking. 

The  fusibility  of  the  enamel  is  another  important  point.  If 
it  is  too  thin,  it  will  sink  into  the  body  and  yield  a  most  imper- 
fect glaze  ;  if  too  glassy,  it  will  overstep  the  modesty  of  nature ; 
if  too  stiff,  it  will  not  fuse  sufiiciently.  The  heat  must  also  be 
carefully  regulated.  If  it  be  too  high,  the  coloring  matters  do 
not  produce  their  full  efi"ect,  indeed  many  of  them  lose  their 
tints  when  very  intensely  heated.  This  is  one  explanation  of 
a  fact,  familiar  to  every  practical  man,  that  the  same  combina- 
tions do  by  no  means  always  furnish  the  same  results. 

The  color  of  the  body  must  always  harmonize  with  that  of 
the  enamel.  It  is  improper  to  make  body  without  coloring 
matter,  for  all  teeth,  which  are  perfectly  healthy,  possess  a 
creamy  or  slightly  yellow  tint,  belonging  to  the  dentine,  which 
is  seen  through  the  enamel,  and  this  must  be  imitated  as  closely 


INCORRUPTIBLE  TEETH.  491 

as  possible  by  the  manufacturer  of  artificial  teeth;  and  he  can 
only  do  it  by  coloring  the  body,  and  then  spreading  a  suitably 
tinted  enamel  over  it. 

The  mechanical  processes  of  making  a  matrix,  moulding  and 
carving  artificial  teeth  do  not  properly  belong  to  a  treatise  like 
this.  They  are  already  described  by  Dr.  Harris,  in  his  Prin- 
ciples  and  Practice  of  Dental  Surgery,  to  which  "we  refer  the 
reader. 

Crucing  or  Biscuiting. — In  regard  to  this  process,  we  have  little 
to  add  to  what  Ave  have  already  said  in  the  chapter  on  porcelain. 

After  drying,  the  blocks  are  subjected  to  a  full  red  heat,  so  as 
to  agglutinate  the  particles  without  fusing  the  paste.  This  may 
be  done  either  in  an  open  charcoal  fire,  or  in  a  mufile.  The  latter 
is  commonly  preferred,  and  the  proper  time  to  withdraw  them  is 
known  by  the  condition  of  test  pieces,  which  are  examined  from 
time  to  time.  When  these  have  become  so  dense  that  they  may 
be  scratched  with  a  knife  with  some  little  difficulty,  the  crucing 
is  complete. 

Any  defects  in  the  form  of  the  teeth  are  now  corrected  by 
filing  and  dressing  up.  The  platinum  pins  are  also  introduced 
by  drilling  holes  in  the  teeth,  and  packing  a  thin  batter  of  paste 
around  the  metal,  after  the  biscuited  blocks  have  been  first 
immersed  in  water. 

Enamelling. — After  the  blocks  are  cruced,  the  enamel  is 
applied  with  a  camel-hair  pencil.  It  must  be  of  the  consist- 
ence of  thin  paste  or  cream,  and  it  must  be  applied  so  as  to 
extend  a  little  beyond  the  edge  of  the  incisors  and  cuspidati,  in 
order  to  obtain  the  translucency  of  the  natural  organs. 

Sometimes  only  two,  but  oftener  three,  different  colors  of 
enamel  are  spread  upon  the  biscuit,  which  must  first  be  tho- 
roughly cleaned.  These  tints  are  a  grayish-blue  for  the  lower 
part  of  the  crowns,  a  yellowish  for  the  portion  nearer  the  gums, 
and  a  rose  red  for  the  gums.  The  red  is  applied  first,  then  the 
yellow,  and  lastly  the  gray.  The  first  tint  should  have  a 
sharply  defined  margin,  but  the  other  two  should  be  blended,  so 
that  they  may  fade  into  one  another. 

Firing  and  Baking. — "VYe  have  already  described  and  figured 
the  furnace  for  baking  teeth.  (See  page  252.)     We  have  now 


492       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

only  to  speak  of  the  method  of  using  it.  The  fire  must  be  clear 
and  strong.  Anthracite  is  usually  preferred  as  fuel.  The  fire 
is  kindled  with  charcoal,  and  after  it  is  fully  ignited,  the  anthra- 
cite is  added  in  portions  till  the  furnace  is  full.  The  coal,  when 
thoroughly  ignited,  should  be  two  or  three  inches  deep  on  the 
top  of  the  mufiie. 

All  the  openings  of  the  furnace  are  closed  and  luted  after  the 
slide  has  been  introduced  into  the  muffle.  When  the  baking  is 
complete,  the  door  of  the  muffle  is  opened,  and  the  slide  par- 
tially withdrawn.  This  point  is  known  by  the  fusion  of  the 
enamel.  As  soon  as  this  has  run  evenly  over  the  teeth,  the 
process  has  been  carried  far  enough.  The  work  is  allowed  to 
remain  until  the  slide  is  cool  enough  to  be  handled.  If  this 
annealing,  or  gradual  cooling  process  should  be  neglected,  the 
teeth  will  be  apt  to  split  and  fly  before  the  blowpipe. 

Composition  and  Preparation  of  Body. — The  formulae  for 
the  body  of  artificial  teeth  are  almost  endless.  Every  one  varies 
them  accordins:  to  his  own  notions  or  the  results  of  his  indivi- 
dual  experience.  We  shall  not  multiply  recipes,  therefore,  but 
confine  ourselves  to  a  very  few. 

Ko.  1. 

Delaware  spar         .         .         .         .  12  oz. 

Silex 2  oz.  8  dwt. 

Kaolin 7|  dwt. 

Titanium 18  to  36  grs. 

No.  2. 

Delaware  spar         .         .         .         .  16  oz. 

Silex ^oz. 

Kaolin  .         .         .         .         .         .  i  oz. 

Titanium 20  to  60  grs. 

"  Put  the  titanium  in  a  large  mortar,  and  grind  until  it  is 
reduced  to  an  impalpable  powder ;  then  add  the  silex,  and  grind 
from  one  to  three  hours,  or  until  there  shall  be  no  perceptible 
grit ;  now  add  the  kaolin,  and  grind  from  thirty  minutes  to  an 


INCORRUPTIBLE  TEETH. 


493 


hour  and  a  half;  and,  lastly,  add  the  spar,  little  by  little,  and 
grind  from  forty  to  sixty  minutes."* 

No.  3. 

Spar 12  oz. 

Quartz 3  "' 

Kaolin 1  " 

Oxide  of  titanium,  12  to  18  grains,  in  proportion  to  the 
depth  of  color  desired. 

No.  4. 

Spar .         40  oz. 

Quartz      .......  8  " 

Kaolin 5  " 

Oxide  of  titanium,  40  to  60  grains.f 

For  the  above  formulse,  I  am  indebted  to  Dr.  A.  A.  Blandy, 
Professor  of  Operative  Dentistry  in  the  Baltimore  College  of 
Dental  Surgery ;  and  I  am  assured  by  him  that  they  are  those 
commonly  used  by  him  in  the  manufacture  of  artificial  teeth, 
and  that  they  have  always  been  successful  in  his  hands.  I  am 
also  indebted  to  him  for  all  the  other  formulae  in  this  chapter 
not  otherwise  credited. 

Colors. — Coloring  matters  vary  very  greatly  in  the  intensity 
of  their  dyeing  power.  Delabarre  gives  the  following  table  of 
oxides,  arranged  according  to  the  depth  of  tint  which  they  im- 
part to  enamels,  and  it  may  be  consulted  with  advantage  by  all 
engaged  in  the  manufacture  of  incorruptible  teeth: — 


TABLE. 

For  4  grammes  are  required 

to  color 

Of  cobalt. 

0.0000535  grammes, 

blue. 

"  platinum. 

6.0000535        " 

grayish-blue. 

"  gold. 

0.0013400 

violet  and  red 

"  bismuth, 

0.0026800 

bluish-gray. 

"  mercury, 

0.0026800        " 

gray. 

"  silver, 

0.0026800 

pale  yellow. 

*  Harris,  Principles  and  Practice  of  Dental  Surgery. 

t  Gum  body,  it  must  be  observed,  is  made  up  without  titanium. 


494       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

Of  iron,  0.0066900  grammes,  yellowish-red. 

"  manganese,  0.0138000         "  gray. 

"  uranium,  0.0535000        "  straw  yellow. 

"  titanium,  0.1070000         "  '  " 

•  "  antimony,  0.2140000        "  yellow. 

It  is  customary  to  reduce  these  oxides  by  previous  fritting. 
This  is  accomplished  by  mixing  them  intimately  with  some 
fusible  silicate,  and  subjecting  them  to  sufficient  heat  to  ag- 
glomerate them  perfectly,  and  to  vitrify  them  upon  the  surface. 
It  is,  in  fact,  a  semivitrifaction. 

The  special  frits  will  now  be  described. 

Blue  Frit. — Mix  intimately,  after  powdering  very  finely,  4 
dwt.  of  platina  sponge  with  |  an  ounce  of  spar  (Boston  spar  is 
recommended,  on  account  of  its  greater  fusibility).  Grind  very 
fine,  and  frit  by  making  up  into  a  ball  with  water,  and  fusing 
very  slightly  upon  a  tile.  While  still  hot,  plunge  it  into  water, 
and,  when  dry,  pulverize  it  very  minutely. 

Yellow  Frit. — Mix  very  intimately  2  dwt.  of  oxide  of  titanium 
with  I  an  ounce  of  spar,  and  heat  it  as  before. 

Gum  Frit. — Purple  of  Cassius,*  8  grains ;  flux,  87  grains ; 
spar,  350  grains.  The  purple  of  Cassius  is  first  to  be  reduced 
to  a  very  fine  powder ;  the  flux  then  added,  by  small  portions 
at  a  time ;  the  mass  being  continually  ground,  to  secure  fine 
comminution  and  perfect  intermixture.  The  spar  is  now  to  be 
added,  also  portionwise,  and  the  grinding  continued  till  the 
whole  is  reduced  to  an  impalpable  powder. 

This  is  now  to  be  placed  in  a  clean  white  Hessian  or  French 
crucible,  lined  with  kaolin  or  powdered  rock  crystal,  made  into 
a  paste  with  a  little  water.  A  cover  is  luted  on  to  prevent 
ashes,  cinder,  or  smoke,  from  contaminating  the  contents.  Heat 
is  then  to  be  applied,  sufficient  to  fuse  the  mixture.  This  fusion 
should  not  run  on  to  perfect  vitrifaction ;  for,  if  the  flux  be  too 
thin,  the  gold  will  sink  through  it,  and  collect  as  a  metallic 
button  at  the  bottom.  The  fusion  being  completed,  the  frit  is 
removed,  and  all  foreign  matter  carefully  separated  from  it.    It 

*  That  made  by  fusing  gold,  tin,  and  silver,  and  dissolving  out  the  silver 
with  nitric  acid,  is  the  proper  purple  for  this  process. 


INCORRUPTIBLE  TEETH.  495 

is  then  pulverized  so  finely  as  to  pass  through  a  No.  9  bolting- 
cloth. 

Another  gum  frit  is  given  by  Dr.  Harris,  composed  as  fol- 
lows :  Metallic  gold,  in  a  state  of  minute  division,  16  grains ; 
flux,  175  grains  ;  spar,  700  grains.     Treat  as  before. 

The  fiux  alluded  to  above  is  composed  of  silex,  4  ounces; 
glass  of  borax,  4  ounces ;  salt  of  tartar,  the  common  carbonate 
of  potash,  1  ounce. 

These  ingredients  are  well  pulverized  and  intimately  mixed. 
They  are  then  introduced  into  a  perfectly  white  Hessian  cru- 
cible, which  is  to  be  covered  with  a  tile  or  a  smaller  crucible, 
well  luted  on,  and  subjected  to  a  heat  sufficient  to  fuse  the  con- 
tents perfectly.  When  this  is  properly  done,  the  result  is  a 
beautifully  transparent  glass,  free  from  any  tint  or  stain  what- 
ever. This  is  to  be  reduced  to  a  fine  powder,  and  put  away  in 
a  closely  stoppered  bottle  for  use. 

Crold  Mixture. — This  preparation,  which  is  also  called  silicate 
of  gold,  is  made  by  dissolving  8  grains  of  pure  gold  in  aqua 
regia,  and  stirring  into  the  solution  15  dwts.  of  spar.  As  soon 
as  it  is  sufficiently  dry,  make  it  into  a  ball,  and  frit  it  gently  on 
a  tile.  Especial  care  must  be  taken  not  to  fuse  this  preparation 
thinly,  or  the  gold  will  melt  and  sink  through  the  flux,  destroy- 
ing the  coloring  matter.  The  frit,  thus  prepared,  is  then  to  be 
reduced  to  powder,  and  set  aside  for  use. 

This  preparation  is  used  for  lowering  the  tone  of  the  titanium 
frits,  which,  without  it,  would  give  too  brilliant  and  decided  a 
yellow  to  the  enamel. 

Enamels. — These  are  more  fusible  than  the  body,  and  must 
be  so  composed  that  they  will  flow  evenly  over  the  biscuit  during 
the  baking  of  the  teeth.  Their  colors  must,  of  course,  vary 
very  greatly,  and  the  skill  of  the  manufacturer  is  shown  in  the 
proper  management  of  his  coloring  materials  to  produce  the 
infinite  variety  of  tints  which  we  see  in  nature.  It  is  therefore 
manifest  that  no  absolute  formulae  can  be  given.  The  best  is 
but  the  expression  of  that  composition  which  is  applicable  to  the 
greater  number  of  cases. 


496       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

Qrayish-Blue  Enamel. 
No.  1. 

Spar 1  oz. 

Blue  frit     .......         5  grs. 

No.  2. 
Boston  spar        .         .         .         .         .         .         2  oz. 

Platina  sponge    .         .         .         .         .         .         i  gr. 


Oxide  of  gold 


Spar  . 
Yellow  frit 
Gold  mixture 


Boston  spar 
Titanium 
Platina  sponge 
Oxide  of  gold 


Boston  spar 
Titanium 
Platina  sponge 
Oxide  of  gold 


Yellow  Enamel. 
No.  1. 


No.  2. 


No.  3. 


No.  3. 

Boston  spar        .         .         .         .         .         .  2  oz. 

Platina  sponge    .         .         .         .         .         .  J  gr. 

Oxide  of  gold i  " 

No.  4. 
Spar  ........         2  oz. 

Platina  sponge |  gr. 

Oxide  of  gold      ...... 


1  <' 

2 


1 

oz. 

4 

grs. 

20 

a 

2 

OZ. 

10 

grs. 

J 

gr- 

1 

u 

2 

2 

OZ. 

14 

grs. 

1 

gr. 

I 

(( 

2 

oz. 

10 

grs, 

1 

2 

gr. 

INCORRUPTIBLE  TEETH.  497 

No.  4. 

Boston  spar  ..... 

Titanium  ...... 

Platina  sponge  ..... 

Oxide  of  gold  .         .         .  ,        . 

Of  the  above  recipes,  the  two  marked  No.  1  were  furnished 
me  by  Dr.  A.  A.  Blandy,  who  has  used  them  extensively,  and 
found  them  to  yield  excellent  results  in  practice.  The  rest  are 
taken  from  the  work  of  Dr.  Harris,  who  observes :  "  No.  2  of 
the  blue,  and  No.  4  of  the  yellow,  will  produce  an  enamel  which 
will  suit  a  larger  proportion  of  cases  than  almost  any  other. 
The  coloring  ingredients  should  be  ground  fine,  with  five  or  six 
dwts.  of  the  spar,  when  the  remainder  of  the  spar  should  be 
added,  a  little  at  a  time,  and  ground  from  thirty  to  forty 
minutes." 

Crum  Enamel. — It  is  customary,  in  the  preparation  of  this 
enamel,  to  grind  the  spar  rather  coarsely,  that  it  may  commu- 
nicate a  granular  appearance  to  the  enamel  after  fusion.  The 
quantity  of  frit  necessary  to  produce  the  proper  effect  must  be 
learned  by  experience.  As  this  varies  in  its  coloring  power,  in 
accordance  with  the  varying  nature  of  the  purple  of  Cassius, 
which  constitutes  its  basis,  to  which  reference  has  already  been 
made,  many  dentists  mix  varying  proportions  of  frit  and  spar, 
and  bake  them  on  different  pieces  of  biscuit,  so  to  feel,  as  it 
were,  for  the  desired  hue. 

A  formula,  which  has  been  found  to  furnish  an  excellent 
color,  is : — 

Gum  frit  ......         30  grs. 

Spar  ......  4  dwt. 

In  this  matter  of  gum  color,  there  is  great  room  for  the  dis- 
play of  individual  skill.  The  hues  of  the  natural  gum  are  very 
various.  Some  gums  are  very  florid ;  others  very  pale ;  some 
nearly  purple ;  some  almost  white.  Many  gums  are  paler  just 
over  the  ridges  of  the  alveoli  and  the  fangs  of  the  teeth.  Some 
have  a  yellowish  suffusion  over  their  basis  of  rose-color.  All 
these  varieties  must  be  imitated  by  the  skilful  manufacturer, 
32 


498       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

and  there  is  but  one  method  to  acquire  the  necessary  skill.  The 
behavior  of  the  oxides  must  be  carefully  studied,  and  a  thorough 
understanding  of  the  effects  of  their  admixture  must  be  acquired. 

Dr.  Hunter  has  introduced  a  new  method  of  manufacturing 
these  dental  substitutes,  and,  not  to  do  him  injustice  by  an 
abridgment,  his  own  account  of  the  process  is  copied  from  his 
paper  in  the  Amei'iean  Journal  of  Dental  Science  for  October, 
1852. 

''  Silex  should  be  of  the  finest  and  clearest  description,  and 
kept  on  hand  ready  ground,  the  finer  the  better. 

"  Fused  Spar  should  be  the  clearest  feldspar,  such  as  is  used 
by  tooth  manufacturers  for  enamels,  completely  fused  in  a  por- 
celain furnace,  and  ground  fine. 

"  Calcined  Borax  is  prepared  by  driving  off  the  water  of 
crystallization  from  the  borax  of  commerce,  by  heating  in  a  cov- 
ered iron  vessel  over  a  slow  fire,  and  it  is  better  to  use  immedi- 
ately after  its  preparation,  as  it  attracts  moisture.  It  should 
be  perfectly  clean  and  white,  and  free  from  lumps. 

"  Caustic  Potassa. — Known  also  as  potassa  fusa. 

"  Asbestos. — Take  the  ordinary  clean  asbestos,  free  it  from 
all  fragments  of  talc  or  other  foreign  substances,  and  grind  fine, 
taking  care  to  remove  any  hard  fragments  that  may  occur. 

"  Granulated  Body. — Take  any  hard  tooth  material  (I  use 
the  following  formula  :  spar  3  oz.,  silex  IJ  oz.,  kaolin  h  oz.), 
and  fuse  completely.  Any  very  hard  porcelain,  wedgewood 
■ware,  or  fine  china,  will  answer  the  same  purpose.  Break  and 
grind  so  that  it  will  pass  through  a  wire  sieve  No.  50,  and  a.ain 
sift  ofi"  the  fine  particles  which  will  pass  through  No.  10  bolting- 
cloth.     It  is  then  in  grains  about  as  fine  as  the  finest  gunpowder. 

'•'•  Flux. — Upon  this  depends  the  whole  of  the  future  opera- 
tions, and  too  much  care  cannot  be  taken  in  its  preparation. 
It  is  composed  of  silex  8  oz.,  calcined  borax  4  oz.,  caustic  po- 
tassa 1  oz.  Grind  the  potassa  fine  in  a  wedgewood  mortar, 
gradually  add  the  other  materials  until  they  are  thoroughly  in- 
corporated. Line  a  Hessian  crucible  (as  white  as  can  be  got) 
with  pure  kaolin,  fill  with  the  mass,  and  lute  on  a  cover,  a  piece 
of  fire-clay  slab,  with  the  same.  Expose  to  a  clear  strong  fire 
in  a  furnace  with  coke  fuel,  for  about  half  an  hour,  or  until  it 


INCORRUPTIBLE  TEETH.  499 

is  fused  into  a  transparent  glass,  which  should  be  clear  and  free 
from  stain  of  any  kind,  more  especially  when  it  is  to  be  used 
for  gum  enamels.  Break  this  down  and  grind  until  fine  enough 
to  pass  through  a  bolting- cloth,  when  it  will  be  ready  for  use. 

'•'■Base. — Take  flux  1  oz.,  asbestos  2  oz.,  grind  together  very 
fine,  completely  intermixing.  Add  granulated  body  1^  oz.,  and 
mix  with  a  spatula  to  prevent  grinding  the  granules  of  body  any 
finer. 

"  Cr^un  Enamels. — No.  1.  Flux  1  oz.,  fused  spar  1  oz.,  English 
rose  40  grains.  Grind  the  English  rose  extremely  fine  in  a 
wedgewood  mortar,  and  gradually  add  the  flux,  and  then  the 
fused  spar,  grinding  until  the  ingredients  are  thoroughly  incor- 
porated. Cut  down  a  large  Hessian  crucible  so  that  it  will  slide 
into  the  muflUe  of  a  furnace,  line  with  silex  and  kaolin  each  one 
part,  put  in  the  material,  and  draw  up  the  heat  on  it  in  a  muffle 
to  the  point  of  vitrifaction,  not  fusion^  and  withdraw  from  the 
muffle.  The  result  will  be  a  red  cake  of  enamel  which  will 
easily  leave  the  crucible,  which,  after  removing  any  adhering 
kaolin,  is  to  be  broken  down  and  ground  tolerably  fine.  It  may 
now  be  tested,  and  then  (if  of  too  strong  a  color)  tempered  by 
the  addition  of  covering.  This  is  the  gum  which  flows  at  the 
lowest  heat,  and  is  never  used  when  it  is  expected  to  solder. 

"  No.  2.  Flux  1  oz.,  fused  spar  2  oz.,  English  rose  60  grains. 
Treat  the  same  as  No.  1.  This  is  a  gum  intermediate,  and  is 
used  upon  platina  plates. 

"  No.  3.  Flux  1  oz.,  fused  spar  3  oz.,  English  rose  80  grains. 
Treat  as  the  above.  This  gum  is  used  in  making  pieces  intend- 
ed to  be  soldered  on,  either  in  full  arches  or  in  the  sections 
known  as  Mock-worJc.  It  is  not  necessary  to  grind  very  fine  in 
preparing  the  above  formulas  for  application. 

"  Covering. — What  is  termed  covering,  is  the  same  as  the  for- 
mulae for  gum,  minus  the  English  rose,  and  is  made  without  any 
coloring  whatever  when  it  is  used  for  tempering  the  above  gums 
which  are  too  highly  colored,  and  which  may  be  done  by  adding, 
according  to  circumstances,  from  1  part  of  covering  to  2  of  gum, 
to  3  of  covering  to  1  of  gum,  thus  procuring  the  desired  shade. 
When  it  is  to  be  used  for  covering  the  base  prior  to  applying 


500       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

the  gum,  it  may  be  colored  with  titanium,  using  from  two  to  five 
grains  to  the  ounce. 

"  Investient. — Take  two  measures  of  white  quartz  sand,  mix 
with  one  measure  of  plaster  of  Paris,  mixing  with  just  enough 
water  to  make  the  mass  plastic,  and  apply  quickly.  The  slab 
on  which  the  piece  is  set  should  be  saturated  with  water  to  keep 
the  material  from  setting  too  soon,  and  that  it  may  unite  with  it. 

"  Cement. — Wax  1  oz.,  rosin  2  oz.  The  proportion  of  this 
will  vary  according  to  the  weather ;  it  should  be  strong  enough 
to  hold  the  teeth  firmly,  and  yet  brittle  enough  to  chip  away 
freely  when  cold.  A  little  experience  will  enable  any  one  to 
prepare  it  properly. 

"Platina,  as  usually  applied,  I  think  objectionable,  wanting 
stifi"ness ;  my  method  of  using  it  is  similar  to  that  proposed  by 
Delabarre,  but  possessing  greater  strength  than  even  his  method, 
and  by  it  can  be  made  as  light  as  a  good  gold  plate  got  up  in 
the  ordinary  way.  I  first  strike  a  very  thin  plate  to  the  cast, 
and  cut  out  a  piece  the  size  of  the  desired  chamber,  taking  care 
not  to  extend  it  forward  to  embrace  the  palatine  artery.  Add 
wax  to  the  plate  for  the  depth  of  cavity,  diminishing  it  neatly  as 
it  approaches  the  alveolar  ridge.  Cement  this  plate  to  the  cast 
and  take  another  metallic  cast,  strike  another  thin  plate  over 
the  whole,  and  solder  throughout  with  an  alloy,  of  gold  twenty- 
two  parts,  platina  two  parts,  or  with  pure  gold.  The  chamber 
thus  formed  is  precisely  the  same  as  '  Cleveland's  Patent  Plate,' 
but  the  space  between  the  plates^  for  which  he  obtained  his  pa- 
tent, is  subsequently  filled  up,  leaving  a  cavity  resembling  Gil- 
bert's, but  with  a  sharper  edge  when  so  desired.  This  space  is 
filled  up  with  base  and  enamel,  and  gives  greater  stiffness  with- 
out the  ugly  protrusion  of  the  struck  chamber.  The  plate  thus 
formed  assimilates  much  more  closely  to  the  palatal  dome,  not 
interfering  with  pronunciation  ;  another  great  advantage  gained 
by  it  is  the  impossibility  of  warping.  I  say  impossibility,  be- 
cause I  have  submitted  plates  so  constructed  to  the  severest 
tests,  and  never  had  them  to  warp.  It  is  well  to  rivet  the  two 
plates  together  before  proceeding  to  solder,  especially  gold 
plates,  and  to  bring  the  heat  carefully  upon  them  ;  once  pre- 
pared there  is  no  danger  of  change  in  the  succeeding  manipu- 


INCORRUPTIBLE  TEETH.  501 

lations.  I  strike  up  the  lower  plate  "witli  a  band  on  the  labial 
edge  about  one-sixteenth  of  an  inch  wide.  This  I  do  by  trim- 
ming the  wax  impression  before  taking  the  plaster  cast,  or  by 
building  a  ridge  of  wax  on  the  plaster  cast  before  taking  the 
metal  casts.  Should  the  band  (or  turned  edge)  flare  out  too 
much,  it  may  readily  be  bent  in  with  a  pair  of  pliers,  &c.  This 
style  of  work  should  not  be  applied  except  where  the  absorption 
may  be  said  to  be  complete. 

"  After  the  plates  are  perfectly  adapted  to  the  mouth,  place 
wax  upon  each,  which  trim  to  the  proper  outline  as  regards 
length  and  contour  of  countenance,  marking  the  proper  occlu- 
sion of  the  jaws  and  the  median  line.  These  waxen  outlines 
are  called  the  drafts,  and  are  carefully  removed  from  the  mouth, 
and  an  articulator  taken  by  which  to  arrange  the  teeth. 

"  When  the  absorption  is  considerable,  and  the  plate  in  conse- 
quence is  rather  flat,  it  is  necessary  to  solder  a  band  or  rim 
along  the  line  where  the  upper  draft  meets  the  plate,  about  one 
sixteenth  or  one-eighth  of  an  inch  wide,  and  fitting  up  against 
the  outline  of  the  draft.  When  the  ridge  is  still  prominent, 
the  block  will  not  of  course  be  brought  out  against  the  lip  so 
much,  and  a  wire  may  be  soldered  on  instead  of  the  wider  band. 
I  think  one  or  the  other  necessary,  as  it  gives  a  thick  edge  to 
the  block,  rendering  it  far  less  liable  to  crack  off  than  if  it  were 
reduced  to  a  sharp  angle ;  it  also  allows  the  edge  of  the  plate 
to  be  bent  in  against  the  gum,  or  away  from  it,  as  circumstances 
may  require,  and  afford,  in  many  cases,  a  far  better  support 
for  the  plates  than  can  be  given  to  one  in  which  the  band 
is  struck  up,  or  the  edge  turned  over  with  pliers,  where  the 
block  must  extend  to  the  edge  of  the  plate.  Some  few  cases  do 
occur,  when  the  band  may  be  struck  as  far  back  as  the  bicus- 
pids with  advantage,  and  some  in  the  lower  jaw  where  it  is  ne- 
cessary to  solder  on  the  band,  but  the  general  practice  is  not  so. 

"  The  upper  teeth  are  first  arranged  on  the  plate  antagonizing 
with  the  lower  draft,  supported  by  wax  or  cement,  or  both. 
Then  remove  the  lower  draft,  and  arrange  the  lower  teeth,  so 
that  the  coaptation  of  the  cutting  edges  of  the  teeth  shall  be 
perfect  as  desired.  The  patient  may  now  be  called  in  again, 
and  any  change  in  the  arrangement  made  to  gratify  his  or  her 


502        MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

taste  or  whim.  Now  place  the  plate,  with  the  teeth  thereon,  on 
their  respective  casts,  oil  the  cast  below  the  plate,  and  apply 
plaster  of  Paris  over  the  edge  and  face  of  the  teeth  and  down 
on  the  cast,  say  an  inch  below  the  edge  of  the  plate.  This  will 
hold  them  firmly  in  their  place  while  you  remove  the  wax  and 
cement  from  the  inside,  and  fit  and  rivet  backs  to  the  teeth. 
"When  backed,  cut  the  plaster  through  in  two  or  more  places, 
and  remove.  Clean  the  plate  by  heating.  Cut  the  plaster  so 
that,  while  it  will  enable  you  to  give  each  tooth  its  proper  posi- 
tion, you  can  readily  remove  it  from  the  teeth  when  they  are 
cemented  to  the  plate.  Adjust  the  sections  of  plaster  and  the 
teeth  in  their  proper  positions.  The  plaster  may  be  held  by  a 
piece  of  soft  wire.  Cement  the  teeth  to  the  plate,  and  strengthen 
the  cement  by  laying  slips  of  wood  half  an  inch  long  along  the 
joint  and  against  the  teeth.  (I  generally  use  the  matches  which 
are  so  plenty  about  the  laboratory.)  llemove  the  sections  of 
plaster,  being  careful  not  to  displace  any  of  the  teeth.  If  it 
be  intended  to  cover  the  strap  with  enamel,  you  should  solder  a 
wire,  after  backing,  and  previous  to  replacing  the  teeth,  along 
the  plate  parallel  with  the  bottom  of  the  straps,  and  about  an 
eighth  or  a  quarter  of  an  inch  from  them. 

"  The  teeth  are  now  backed  and  cemented  to  the  plate,  and 
present  an  open  space  between  the  plate  and  the  teeth,  which  is 
to  be  filled  up  with  the  base,  using  it  quite  wet  to  fill  up  the  small 
interstices,  filling  in  the  rest  as  luird  and  dry  as  i^ossible.  Fill 
the  cavity  between  the  plates  in  the  same  manner,  and  oil  the 
edge.  Oil  the  surface  of  the  base,  envelop  in  the  investient 
(precisely  as  you  would  put  an  ordinary  job  into  plaster  and 
sand  for  soldering),  and  set  on  a  fire-clay  slab  previously  saturated 
with  water.  When  hard,  chip  away  the  cement,  cooling  it  if 
necessary  with  ice,  until  it  is  perfectly  clean.  Along  the  joints 
place  scraps  and  filings  of  platina  very  freely,  and  cover  all  the 
surface  you  wish  to  enamel  with  coarse  filings,  holding  them  to 
their  place  by  borax  ground  fine  with  water.  Apply  pure  gold 
as  a  solder  quite  freely,  say  two  dwt.  or  more  to  a  single  set. 
Put  in  a  mufile,  and  bring  up  a  gradual  heat  until  the  gold  flows 
freely,  which  heat  is  all  that  Avill  be  needed  for  the  base ;  with- 
draw, and  cool  in  a  muffle.     Remove  the  investient  and  fill  up 


INCORRUPTIBLE  TEETH.  503 

all  crevices  and  interstices  not  already  filled,  with  covering  No. 
2 ;  cover  the  straps  and  base  with  the  same,  about  as  thick  as  a 
dime,  and  cover  this  with  gum  No.  2,  about  half  that  thickness. 
At  the  same  time  enamel  the  base  in  the  chamber,  and  cover 
with  thick  soft  paper.  Set  the  plate  down  on  the  investient  on 
a  slab,  with  the  edges  of  the  teeth  up.  Fuse  in  a  mufile,  and  the 
work  is  completed.  Blemishes  may  occur  in  the  gum  from  a 
want  of  skill  in  the  manipulation  ;  should  such  occur,  remedy  by 
applying  gum  No.  1. 

"  Should  the  patient  object  to  the  use  of  platina  as  a  base,  the 
work  can  be  made  as  above  on  an  alloy  of  gold  and  platina  20 
carats  fine,  and  soldered  with  pure  gold,  &c.  as  above.  In  all 
cases,  however,  where  it  is  used,  the  upper  plate  should  be  made 
as  I  have  described  above,  but  with  platina  any  kind  of  plate 
can  be  used. 

"  Ordinary  Alloy. — Blocks  may  be  made  and  soldered  to  the 
ordinary  plate  if  the  absorption  is  sufficient  to  require  much  gum, 
without  any  platina.  Arrange  the  teeth  on  wax  on  the  plate,  fill 
out  the  desired  outline  of  gum,  and  apply  plaster  a  quarter  of 
an  inch  thick  over  the  face  of  teeth,  wax  and  cast.  When  hard, 
cut  it  into  sections  (cutting  between  the  canines  and  bicuspids), 
remove  the  wax  from  the  plate  and  teeth,  bind  the  sections  of 
the  plaster  mould  thus  made  to  their  places  with  a  wire,  oil  its 
surface  and  that  of  the  plate,  fill  in  the  space  beneath  the  teeth 
with  the  base,  wet  at  first,  but  towards  the  last  as  hard  and  dry 
as  possible,  and  thoroughly  compacted.  Trim  to  the  desired 
outline  on  the  inside,  oil  the  base,  and  fill  the  whole  palatal  space 
with  investient,  supporting  the  block  on  its  lingual  side.  Re- 
move the  plaster  mould  and  cut  through  the  block  with  a  very 
thin  blade  between  the  canines  and  bicuspids.  Take  the  whole 
job  off  of  the  plate,  and  set  on  a  fire-clay  slab  with  investient, 
the  edges  of  the  teeth  down  ;  bring  up  the  heat  in  a  muffle  to  the 
melting  point  of  pure  gold.  When  cold,  cover  and  gum  with 
No.  3  gum  and  covering. 

"  Another  mode  is  to  back  the  sections  with  a  continuous  strap 
(using  only  the  lower  pin),  fill  in  the  base  from  the  front,  use 
covering  and  gum  No.  3,  and  finish  at  one  heat.  When  the 
blocks  are  placed  upon  the  plate,  the  other  pin  is  used  to  fasten 


504       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

the  gold  back,  which  is  soldered  to  it,  and  the  platina  half-back ; 
neither  of  these  backs  need  be  very  heavy,  as  soldering  the  two 
together  gives  great  strength  and  stiffness.  Very  delicate  block- 
work  can  be  made  in  this  way,  and  it  is  applicable  also  where 
a  few  teeth  only  are  needed. 

"  A  very  pretty  method,  where  a  section  of  two  or  four  teeth 
(incisors)  is  needed  and  only  a  thin  flange  of  gum,  is  to  fit  gum 
teeth  into  the  space,  unite  by  the  lower  platina  with  a  continuous 
back,  and  unite  the  joint  with  gum  No.  3.  A  tooth  left  un- 
gummed  by  the  manufacturer  would  be  best  for  the  purpose. 
The  same  may  be  applied  to  blocks  for  a  full  arch,  remembering 
not  to  depend  entirely  upon  platina  backs. 

"  The  method  I  prefer  for  full  arches  on  ordinary  plate,  is  to 
take  a  ribbon  of  platina  a  little  wider  than  the  intended  base, 
and  of  the  length  of  the  arch,  cut  it  nearly  through  in  five 
places,  viz.  between  the  front  incisors,  between  the  lateral  in- 
cisors and  canines,  and  between  the  bicuspids.  Adapt  it  to  the 
form  of  the  alveolar  ridge  with  a  hammer  and  pliers,  and  swage 
on  the  plate  along  where  the  teeth  are  to  be  set.  Solder  up  the 
joints  with  pure  gold,  and  proceed  to  back  the  teeth,  &c.,  as  be- 
fore ;  making  preparations  for  fastening,  and  removing  the  slip 
of  platina  from  the  gold  plate  before  enveloping  in  the  inves- 
tient,  when  proceed  as  before. 

"  When  the  teeth  are  arranged,  insert  four  platina  tubes  about 
one  line  in  diameter,  two  between  the  molars,  and  two  between 
the  cuspidati  and  bicuspids,  and  solder  to  the  platina  base. 
These  are  designed,  after  the  teeth  are  finished,  to  be  the 
means  of  fastening  to  the  gold  plate,  either  by  riveting  in  the 
usual  way,  or  by  soldering  pins  to  the  gold  plate  passing  up 
through  the  tubes,  fastening  with  sulphur  or  wooden  dowels. 
By  these  methods  we  are  enabled  to  readily  remove  the  block 
and  repair  it,  should  it  meet  with  any  accident,  and  also,  in  case 
absorption  should  go  on,  to  restrike  the  plate,  or  to  lengthen  the 
teeth.  The  rim  should  be  put  on  the  gold  plate  after  the  block  is 
finished  ;  it  gives  great  additional  strength  and  a  beautiful  finish. 

"  Memoranda. — In  preparing  material,  always  grind  dry,  and 
the  most  scrupulous  cleanliness  should  attend  all  the  manipula- 
tions.    In  all  cases  where  heat  is  applied  to  an  article  in  this 


INCORRUPTIBLE  TEETH.  505 

system,  It  should  be  raised  gradually  from  the  bottom  of  the 
muffle  and  never  run  into  a  heat.  Where  it  is  desired  to 
lengthen  any  of  the  teeth,  either  incisors  or  masticators,  or  to 
mend  a  broken  tooth,  it  may  be  done  with  covering,  properly 
colored  with  platina,  cobalt,  or  titanium.  " 

"  In  repairing  a  piece  of  work,  wash  it  with  great  care,  using 
a  stiiF  brush  and  pulverized  pumice-stone.  Bake  over  a  slow 
fire  to  expel  all  moisture,  and  wash  again,  when  it  will  be  ready 
for  any  new  application  of  the  enamel.  Absorption,  occurring 
after  a  case  has  been  some  time  worn,  by  allowing  the  jaws  to 
close  nearer,  causes  the  lower  jaw  to  come  forward  and  drive  the 
upper  set  out  of  the  mouth.  By  putting  the  covering  on  the 
grinding  surface  of  the  back  teeth  in  sufficient  quantities  to 
make  up  the  desired  length,  the  coaptation  of  the  denture  will 
be  restored,  and  with  it  the  original  usefulness. 

"Any  alloy  containing  copper  or  silver  should  not  be  used  for 
solder  or  plate,  if  it  is  intended  to  fuse  a  gum  over  the  lingual 
side  of  the  teeth,  as  it  will  surely  stain  the  gum.  Simple  platina 
backs,  alone,  do  not  possess  the  requisite  stiifness,  and  should 
always  be  covered  on  platina  with  the  enamel,  and  on  gold  with 
another  gold  back.  In  backing  the  teeth,  lap  the  backs  or 
neatly  join  them  up  as  far  as  the  lower  pin  in  the  tooth,  and 
higher,  if  admissible,  and  in  soldering  be  sure  to  have  the  joint 
so  made  perfectly  soldered. 

"  As  the  work  on  platina  plate  presents  fewer  difficulties  to  the 
tyro,  it  would  be  well  to  gain  experience  upon  that  kind  of 
work  before  attempting  its  application  to  gold  bases.  The 
proper  tooth  for  this  work  is  not  yet  in  the  market,  but  I  think 
will  be  ere  long.  A  tooth  finished  at  one  heat  by  the  manufac- 
turer is  best,  although  any  tooth  may  be  used  that  has  been 
painted  at  a  higher  heat  than  the  melting  point  of  gold,  being 
careful  not  to  use  any  tooth  in  which  gold  may  have  been  incor- 
porated, as  it  will  change  color  in  the  fire.  A  tooth  with  a 
natural  shaped  crown,  but  thinner  than  the  natural  tooth,  with 
the  platina  pins  at  a  point  that  will  allow  of  the  back  being 
covered  without  being  clumsy,  is  wanted,  and  likewise  a  tooth 
resembling  the  natural  tooth,  except  that  the  molars  be  made 
with  one  conical  fang  similar  to  a  dens  sapientiie." 


606       MATERIALS  USED  IN  MAKING  INCORRUPTIBLE  TEETH. 

Dr.  Allen's  formula  are  as  follows : — 
■  For  the  Base. — Silex,  2  ounces ;  flint  glass,  1  ounce  ;  borax, 

1  ounce ;  wedgewood,  1|-  ounce  ;  asbestos,  2  drachms  ;  feldspar, 

2  drachms ;  kaolin,  1  drachm ;  intermixed  or  underlined  with 
scraps  of  gold  or  platina. 

■  For  the  Enamel. — Feldspar,  J  an  ounce  ;  white  glass,  1  ounce  ; 
oxide  of  gold,  |-  grain.  The  latter  ingredient  gives  the  gum 
color. 


I 


IJVDEX. 


*^*  Those  ■words  priuted  in  small  capitals  indicate  tlie  heads  of  chapters. 


Acetic  acid,  76 
Acid,  acetic,  76 

auric,  306 

benzoic,  80 

butyric,  77 

caproic,  78 

caprj'Iic,  79 

carbazotic.     (See  Picric.) 

choleic,  73 

cbolic,  85 

conjugated,  67 

cupric,  375 

doeglic,  85 

eliiidic,  84 

formic,  76 

glycocliolic,  71 

hippuric,  67 

hydrochloric,  121 

Lj'drofluosilicic,  463 

inosic,  71 

hictic,  81 

leucic,  57 

lithofellic,  85 

margaric,  83 

metacetonic,  77 

oenantbylic,  79 

oleic,  84 

osuiic,  418 

oxalic,  75 

picric,  67 

propionic.     (See  Metacetonic.) 

sebacic,  80 

silicic,  451 

stearic,  91 

taurocholic,  72 

titanic,  480 

uric,  68 

urobenzoic.     (See  Hippuric.) 

valerianic,  78 


Acids  generated  in  indigestion,  131 
Adularia,  471 
Albite,  472 

Albumen,  change  of,  during  digestion, 
130 

coagulated,  35 

combinations  of,  34 

composition  of,  36 

preparation  of,  36 

quantitative  estimation  of,  37 

soluble,  34 

tests  for,  36 

Tarieties  of,  33 

vegetable,  28 
Albuminate  of  soda,  35 
Albuminose,  130 

Albuminous   group   of    animal    sub- 
stances, 28 
Alcohol  as  fuel,  261 
Aldehydes,  73 
Allantoine,  63 

Allen's  formuIiB  for  artificial  teeth,  500 
Alumina,  455 

a  constituent  of  the  body,  21 

silicates  of,  457 

sulphate  of,  456 
Aluminum,  454 

chloride  of,  456 
Amalgamation  of  gold,  282 

silver,  325 
Amalgam  question,  441 
Amalgams  for  mirrors,  401 

teeth,  444 
Amides,  74 
Ammones,  88 

Ammonia,  constitution  of,  88 
Anntase,  481 
Aniline,  53 
Anthracite,  266 
Arsenic,  21 


r>08 


INDEX. 


B. 

Baking  teeth,  491 
Bell  metal,  377 
Benzoic  acid,  80 

relations  to  hippuric  acid, 
C8 
Bile,  132 

chemical  composition  of,  133 
influence  on  digestion,  141 
metamorphosis   of,    in   intestines, 

147 
morbid  changes  of,  134 
origin  of,  135 
pigment,  102 
quantity  of,  135 
relation  of,  to  obesity,  130 

respiration,  136 
Bilifulvin,  103 
Bilin,  72 
Biliphtein,  103 
Biliverdin,  108 
Biscuit,  473 
Bismuth,  412 

alloys  of,  414 
bromide  of,  415 
chloride  of,  415 
iodide  of,  415 
metallic,  412 
metallurgy  of,  412 
nitrate  of,  416 
oxides  of,  413 
phosphate  of,  410 
phosphuret  of,  414 
sulphate  of,  415 
sulphuret  of,  414 
Blowpipe,  237 

Black's,  239 
Cronstedt's,  237 
directions  for  using,  244 
Elliott's,  246 
flame  of,  243 
Gahn's,  239 
material  for,  240 
Mitscherlich's,  230 
Parmly's,  245 
self-acting,  245 
table,  247 
Wollaston's,  238 
Body,  composition  and  jjreparation  of, 
492 
Hunter's,  499 
Borax,  465 

glass  of,  465 
Brass,  378 

solder,  378 
Britannia  metal,  401 
Bronze,  '376 


Brookite,  481 
Butyral,  73 
Butyric  acid,  77 

physiological  relations  of, 
78 
Butyrone,  74 


Calcium  a  constituent  of  the  body,  19 
Calculi,  biliary,  135 

formation  of,  135 
Calomel  stools,  151 
Cannon  metal,  377 
Caproic  acid,  78 
Caprylic  acid,  79 
Carats,  299 

Carljazotic  acid.     (See  Pici-ic  Acid.) 
Carbon  an  element  of  the  body,  19 
Casein,  coagulation  of,  44 
composition  of,  45 
digestibility  of,  130 
physiological  relations  of,  46 
preparation  of,  46 
quantitative  analysis  of,  46 
soluble,  43 
tests  of,  46 
vegetable,  28 
Cassius,  purple  of,  307 
Cement,  AVillis's,  261 
Cementum,  analysis  of,  154 
Chalcolite,  483 
Charcoal,  peat,  269 
wood,  267 
Chlorine  a  constituent  of  the  body,  19 
Choleic  acid,  73 
Cholepyrrhin,  102 
Cholesterin,  95,  133,  135,  140 
Cholic  acid,  85 

formed  from  fat,  86 
tests  for,  86 
Chondrin,  composition  of,  52 

physiological  relations  of,  53 
preparation  of,  53 
Chylopoine,  142 
Clays,  analysis  of,  467 

classification  of,  468 

composition  of,  469,  470 

distribution  of,  466 

effect  of  heat  on,  468 

for  Hessian  crucibles,  255 

impurities  of,  468 

modes  of  increasing  the  pliancy 

of,  476 
origin  of,  466 
refractory,  254 
Coal,  bituminous,  266 

chemical  composition  of,  266 


INDEX. 


509 


Coal,  geological  situation  of,  265 
mineral,  265 
varieties  of,  265 
Cobalt,  oxide  of,  486 
Coinage,  gold,  table  of,  316 

silver,  table  of,  347 
Coke,  269 

Conjugated  acids,  67 
Copper,  363 

acetates  of,  386 

a  component  of  the  body,  21 

alloys  of,  376 

metallurgy  of,  369 
ammonio-chloride  of,  381 
arsenites  of,  386 
black  oxide  of,  373 

salts  of,  383 
borate  of,  386 
bromide  of,  381 
carbonate  of,  385 
chlorides  of,  379 
dioxide  of,  372 

salts  of,  382 
fluoride  of,  381 
hydruret  of,  376 
hyposulphate  of,  384 
iodide  of,  381 
metallic,  371 
nitrate  of,  385 
nitruret  of,  376 
ores  of,  364 

dry  assay  of,  366 
metallurgy  of,  365 
oxides  of,  372 
peroxide  of,  375 
phosphate  of,  385 
phosphuret  of,  376 
silicate  of,  386 
sulphate  of,  383 
sulphurets  of,  375 
Creatine,  54 
Creatinine,  55 
Crucibles,  254 

Anstey's,  258 
Beaufaye's,  258 
black-lead,  258 
characters  of  good,  256 
clay,  258 

composition  of,  257 
examination  of,  257 
Hessian,  258 
iron,  258 
London,  258 
platinum,  259 
porcelain,  258 
silver,  258 
Crucihg,  491 


Cupellation  of  gold,  282 
silver,  330 

on  the  large  scale, 
383 
Cupels,  259 
Cupric  acid,  375 

D. 

Dentine,  analysis  of,  154 

Digestion,  105 

accelerated  by  fat,  139 
diminished    by   acids,    &c., 
139 

GASTRIC,   119 

influence  of  nervous  system 
on,  129 

INTESTINAL,   132 

Dcieglic  acid,  85 
Drivelling,  197 

E. 

Eliiidic  acid,  84 

Elements,  proximate,  of  the  body,  18 

ultimate,  17  ^ 

Enamel,  analysis  of  the,  154,  155 

artificial,  formulas  for,  496 
Enamelling,  491 
Extractive  matters,  104 


Fat,  metamorphosed  in  liver,  139 
origin  of,  92 
relations  to  bile,  138 

muscular  activity,  92 
nutrition,  138 
respiration,  93 
sexual  functions,  92 
uses  of,  93,  144 
Faeces  after  iron,  151 

after  mercury,  151 
chemistry  of,  149 
of  infants,  151 
Feldspar,  470 

common,  472 
glassy,  471 
soda,  472 
Fibrin,  boiled,  39 

coagulated,  37 
composition  of,  39 
muscular.     (See  Syntonin.) 
physiological  relations  of,  41 
preparation  of,  40 
relations  to  tissue,  41 
spontaneously  coagulated,  37 
tests  for,  40 
vegetable,  28 
Fire-lute,  Faraday's,  260 


510 


INDEX. 


Fire-lutev  Parker's,  260 
Watts's,  260 
•  Flame,  oxidating,  248 
reducing,  243 
structure  of,  241 
Fluorine  a  constituent  of  the  body,  20 
Food,  albuminous,  112 

comparatiTe  value   of  vegetable 

and  animal,  115 
deficiency  of,  117 
gelatinous,  112 
oleaginous,  112 
Prout's  classification  of,  111 
respiratory,  113 

value  of  diflFerent  ar- 
ticles as,  115 
saccharine,  112 
Formic  acid,  76 
Fowlerite,  485 
Frit,  blue,  494 
gum,  494 
yellow,  494 
flux  for,  495 
Fuel,  261 

choice  of,  274 

effect  of  heat  on,  267 

for  lamps,  261 

influence  of  time  on,  273 

mode  of  estimating  the  value  of, 

278 
proper  size  of,  275 
table  of  relative  value  of  different 
kinds  of,  271 
Furnaces,  248 

blast,  252 

Barron's,  253 
cupelling,  250 
for  baking  teeth,  252 
measurement  of  heat  of,  275 
reverberating,  250 
wind,  248 
Fusible  metal,  407 
Fusion-points,  table  of,  278 

G. 
Gastric  fistula,  how  to  establish,  120 
juice,  119 

amount  of,  128 

artificial,  124 

chemical    characters    of, 

120 
modes  of  obtaining,  119 
physical    characters    of, 
120 
Gelatin,  sugar  of,  58 
uses  of,  114 
Gelatinous  group,  50 


Gelatinous  group,  changes   of,  in  di- 
gestion, 130 
Globulin,  41 

composition  of,  42 
preparation  of,  42 
physiological  relations  of,  42 
Glucose,  96 

in  the  intestinal  canal,  146 
tests  for,  97 
Gluten,  composition  of,  47 
preparation  of,  48 
Glutin,  composition  of,  51 

physiological  relations  of,  52 
preparation  of,  51 
reactions  of,  50 
Glycine,  58,  140 
Glycocoll,  58 
Glycocholic  acid,  71 
Gold,  278 

alloys  of,  312 

cupellation  of,  287 
for  plate  work,  314 
metallurgy  of,  284 
amalgamation  of,  282 
bromides  of,  324 
chlorides  of,  322 
coins   of,   chemical   composition 

of,  316 
crystals  of,  278 
foil,  302 
fusion  of,  with  galena,  286 

black     oxide     of 
manganese,  286 
oxidating   re- 
agents, 284 
sulphur,  280 
sulphuret  of  anti- 
mony, 285 
geographical  distribution  of,  280 
geological  situations  of,  279 
iodide  of,  324 
leaf,  302 
metallic,  303 
mixture,  495 
ores  of,  metallurgy  of,  280 

amalgama- 
tion, 282 
cupellation, 

282 
fusion,  282 
stamping, 

281 
washing, 
281 
oxides  of,  305 

preparation  of,  for  co- 
loring porcelain,  305 


INDEX. 


511 


Gold,  parting  of,  from  silver,  288 

concentrated,  288 
dry,  288 

by  sulphur,  289 
wet,  219 
by  aqua  regia,  298 
nitric  acid,  289 
on  the  large 
scale,  292 
sulphuric   acid, 
295 

Pettenko- 
fer's  views 
of,  297 
phosphates  of,  311 
pigments  for  painting  porcelain, 

311 
platinum  in,  287 
scorification  of,  284: 
sponge,  308 
sulphurets  of,  311 
Goldbeating,  300 
Guanine,  64 
Gum  enamels,  497 

Hunter's     formulae    for, 
499 

H. 
Hfematin,  100 
Hsematoidin,  101 
Haloids,  87 

Heat,  influence  of,  on  chemical  attrac- 
tion, 235 
physical  states  of 
bodies,  236 
Hindoos,  rice  ordeal  of,  195 
Hippuric  acid,  67 

relations  to  benzoic  acid, 
68 
Hunter's  formulEe,  498 
Hydrocarbons,  96 

Hydrochloric  acid,  a  constituent  of  gas- 
tric juice,  121 
Hydrofluosilicic  acid,  453 
Hydrogen  a  constituent  of  the  body,  19 

I. 

Inosic  acid,  71 

Intestinal  canal,  contents  of,  146 
gases  of,  1 47 
juice,  144 

chemical  characters  of, 

145 
digestive  powers  of,  145 
Iron,  a  constituent  of  the  body,  21 

green  stools  after  the  administra- 
tion of,  150 


Iron,  titaniferous,  481 

Iserine,  481 

Jewellery,  composition  of,  321 

K. 

Kaolin,  469 

composition  of,  469 
localities  of,  469 
preparation  of,  489 

Eo-emnitz  white,  409 


Lactic  acid,  81 

in  blood,  83 

gastric  juice,  82,  121 
intestines,  146 
muscles,  83 
preparation  of,  81 
Lamps,  240 

Berzelius's  blowpipe,  241 
dentist's,  240 
fuel  for,  242 
Russian,  245 
Lead,  403 

acetate  of,  410 
a  constituent  of  the  body,  21 
alloys  of,  407 
borate  of,  411 
bromide  of,  408 
carbonate  of,  409 
chloride  of,  408 
chromates  of,  411 
fluoride  of,  408 
iodide  of,  408 
metallic,  405 
metallurgy  of,  403 
nitrate  of,  410 
oxides  of,  405 
phosphate  of,  410 
phosphuret  of,  407 
red,  400 
sulphate  of,  410 
sulphuret  of,  406 
white,  409 
Legumin,  composition  of,  48 
preparation  of,  49 
Leucic  acid,  57 
Leucine,  56 
Lignite,  265 

Lime,  oxalate  of,  a  normal  constituent 
of  urine,  75 
relations   to   respira- 
tion, 75 
Lipoids,  96 
Lipyl,  oxide  of,  89 

salts  of,  89 
Lithofellic  acid,  85 


512 


INDEX. 


Liver,  function  of,  142 
Lutes.    (See  Fire-lutes.) 

M. 

Magnesium,  a  constituent  of  the  body, 

21 
Magnus,  green  substance  of,  429 
Manganese,  a  constituent  of  the  body, 
21 
oxide  of,  for  coloring  por- 
celain, 479 
preparation     of, 
485 
Manganocalcite,  487 
Margaric  acid,  83 
Margarin,  91 
Meconium,  151 
Melanin,  102 
Menakan  ore,  481 
Mercury,  438 

amalgams  of,  444 
bromides  of,  445 
chlorides  of,  444 
effects  of,  on  the  system,  446 
iodides  of,  445 
metallic,  441 
metallurgy  of,  439 
mines  of,  438 
nitrates  of,  446 
nitruret  of,  443 
oxides  of,  442 
phosphates  of,  446 
phosphuret  of,  443 
poisonous  dose  of,  449 
sulphates  of,  446 
sulphurets  of,  443 
Metacetonic  acid,  77 
Milk,  composition  of,  114 

globules  of,  their  structure,  46 
sugar  of,  99 
Models,   metallic,    suitable   alloys   for, 

377,  389,  408,  414 
Mouldering  of  clays,  471 
Mucin,  224 
Mucus,  222 

albumen  in,  227 
analysis  of,  228 
buccal,  227 
morbid  nasal,  228 
morphological   constituents  of, 

223 
nasal,  226 
origin  of,  229 
pulmonary,  226 
quantity  of,  229 
reaction  of,  223 
salts  of,  227 


Mucus,  supposed    action     on     starch, 

184,  190 
Murexide,  69 
Music  metal,  401 

N. 
Nitriferes  artificielles,  461 
Nitriles,  74 

Nitrogen  a  cause  of  the  instability  of 
animal  compounds,  24 
a  constituent  of  the  body,  19 
Nitrogenous  basic  bodies,  53 
non-nitkogenous  acids,  73 

0. 

Octahedrite,  481 
(Enanthylic  acid,  79 
Oleic  acid,  84 

in  portal  blood,  138 
Olein,  91 

Organic  compounds,  causes  of  instability 
of,  25 
mode    of   union  of 

elements  of,  22 
illustrated   by   pla- 
tinum salts,  430 
Osmium,  418 
Oxalate  of  lime,  75 
Oxalic  acid,  75 

Oxygen,  a  constituent  of  the  body,  19 
introduced  into  the  stomach  in 
the  saliva,  193 


Pancreatic  juice,  142 

chemistry  of,  142 
digestive  power  of,  143 
uses  of,  145 
Parting.     (See  Gold.) 
Peat,  264 
Pepsin,  124 

preparation  of,  125 
Schmidt's  notion  of,  127 
Peptones,  129 
Petinine,  53 
Pettenkofer's  test  for  bile,  86 

fallacies    of, 
138 
Pe-tun-tze,  469 
Pewter,  400 
Phosphorus,  a  constituent  of  the  body, 

19 
Picoline,  53 
Picric  acid,  67 
Pigments,  animal,  100 

for  porcelain,  478 
Pitchblende,  483 


INDEX. 


613 


Plate.     (See  Silver.) 

Plate-work,  suitable  alloys  for,  314 

Platinum,  4]  6 

action  of  finely  divided,  on 

gases,  425 
alloys  of,  428 

metallurgic  treat- 
ment of,  422 
bichloride  of,  436 
binoxide  of,  427 
black,  425 
chloride  of,  429 
coins  of,  424 
compound  bases  containing, 

430,  et  seq. 
geographical  distribution  of, 

417 
iodides  of,  436 
native,  417 
nitrate  of,  437 
nitruret  of,  428 1' 
oxide  of,  426 
phosphuret  of,  427 
preparation  of,  417 
spongy,  425 
sulphate  of,  437 
sulphuret  of,  427 
value  of,  424 
POECELAIN,  473 

analysis  of,  478 
contraction  of  inbaking,477, 

490 
density  of,  477 
glaze  of,  476 
history  of,  473 
manufacture  of  at   Sevres, 

475 
pigments  of,  478,  493 

Linderer's  form- 
ula for,  487 
structure  of,  477 
tender,  474 
true,  475 
varieties  of,  474 
Portal  blood  compared  with  hepatic,  138 
Potassa,  458 

nitrate  of,  460 

artificial,  460 
preparation  of,  459 
Propionic  acid.   (See  Metacetonic  Acid.) 
Protein,  behavior  of  reagents  towards, 
32 
compounds,  29 

Lehmann's  objections  to  Mul- 
der's theory  of,  31 
Mulder's  view  of,  30 
teroxide  of,  49 

33 


Proximate  elements,  28 
Ptyalin,  159 

Berzelius's  process  for  obtain- 
ing, 166 
Lehmann's  process  for   obtain- 
ing, 167 
Simon's  process  for  obtaining, 

167 
reactions  of,  167 
Wright's,  168 
Ptyalism,  199 

iodic,  203 
mercurial,  199 

analysis  of  fluid  of, 
202 
occasioned  by  other  reagents, 
204 
Putrefaction,  Helmholtz's  experiments 
on,  26 
Lewis's  experiments  on,  27 
Pyrometer,  Daniell's,  276 

Wedgewood's,  275 
Pyrosis,  fluid  of,  197 

Q. 

Quartation,  290 
Quartz,  473 

preparation  of,  473,  489 
Queen's  metal,  401 

R. 

Radicals,  compound,  24 

Ranula,  fluid  of,  195 

Reiset,  yellow  salt  of,  430 

Resinous  acids,  85  , 

Rock  crystal,  473 

Rutile,  481 

S. 
Saliva,  158 

alkalinity  of,  variations  in  the, 

162,  181 
analysis  of,  177 

analysis  of,  Lehmann's  method, 
175 
Simon's  method,  175 
Wright' s  me  thod,  1 73 
varieties  of,  165 
acid,  211 

relations   of  to  inflamma- 
tion, 212 
acrid,  217 
albuminous,  207 
alkaline,  214 
biUous,  208 
bloody,  210 
calcareous,  214 


514 


INDEX. 


Saliva,  changes  of  in  Tarious  diseases, 
220 
I         deficient,  194 

digestive  action  of,  181 

on     albumi- 
nous food, 
189,  192 
on     starch, 
181 

as    com- 
pared with  other 
animal  fluids,  185 
relation     of 
acidity  to,  187 
elective     elimination     through, 

179 
etymology  of,  158 
fatty,  204 
fetid,  216 
gelatinous,  219 
milky,  221 

modes  of  obtaining  for  experi- 
ment, 158 

MORBID  CHANGES  OF,   194 

morphological  elements  of,  159 
oxygen  absorbed  by,  172 
parotid,  163 

cause  of  alkaline   reac- 
tion of,  164 
specific  gravity  of,  163 
physiology  of,  179 

Bernard's     views 

of,  183 
Liebig's  views  of, 

193 
Wright's  views  of, 
181 
puriform,  216 
quantity  of,  159 
reaction  of,  162 
redundant,  196 
saline,  215 
specific  gravity  of,  161 

affected  by  in- 
gesta,  161 
tubmaxillary,  164 
sulphocyanogen  in,  170 

variations  of, 
171 
sweet,  206 
urinary,  218 

varieties     of     from     different 
glands,  163 
Salivart  calculi,  231 

analysis  of,  231 
Salivary  diastase,  191 
Sal  prunelle,  462 


Salts,  composition  of,  87 
Sarcina  ventriculi,  148,  198 
Sarcosine,  57 
Sebacic  acid,  80 
Silicic  acid,  451 
Silicon,  450 

a  constituent  of  the  body,  19 
bromide  of,  453 
chloride  of,  453 
oxide  of,  451 
preparation  of,  450 
sulphuret  of,  453 
Silver,  325 

alloys  of,  345 

metallurgic  treatment 
of,  329 
by  cupellation,  330 
by     crystallization, 

335 
by  humid   process, 
336 

in    presence      of 
mercury,  340 
by  liquation,  335 
by  scorification,  329 
arseniate  of,  363 
borate  of,  362 
bromide  of,  367 
carbonate  of,  362 
carburets  of,  345 
chlorate  of,  362 
chloride  of,  356 

reduction  of  in  the 

dry  way,  337 
reduction  of  in  the 
wet  way,  338 
chromate  of,  363 
coins,  table  of,  347 
fluoride  of,  358 
fulminating,  343 
German,  378 
hyposulphate  of,  339 
iodate  of,  362  '^ 

iodide  of,  337 
metallic,  341 
native,  325 
nitrate  of,  361 
nitrite  of,  361 
ores  of,  325 

amalgamation  of,  326 
Mexican  method, 

326 
Saxon  method,  327 
metallurgy  of,  326 
smelting  of,  328 
oxide  of,  342 
perchlorate  of,  362 


I 


INDEX. 


515 


Silver,  periodate  of,  362 
peroxide  of,  344 
phosphates  of,  361 
phosphuret  of,  345 
plate,  355 
siliciuret  of,  345 
silico-fluoride  of,  358 
subchloride  of,  357 
suboxide  of,  342 
sulphate  of,  358 
sulphite  of,  359 
sulphuret  of,  344 
Soda,  463 

carbonate  of,  464 
Sodium,  463 

an  element  of  the  body,  20 
Solder,  gold,  315 
silver,  346 
brass,  379 
Speculum  metal,  377 
Sphene,  480 

Starvation,  phenomena  of,  118 
Stearin,  91 

Substitution  theory,  24,  25 
Succinic  acid,  79 
Sugar,  convertible  into  fat,  114 
destination  of,  113 
in  the  liver,  139 
Sulphocyanide  of  potassium,  determina- 
tion of,  170 
influence  on 
digestion,  192 
physiologi- 
cal use  of,  193 
quantity  of 
affected  by  ingesta,  171 
Sulphur,  a  constituent  of  the  body,  19 
Surcharge,  291 
Syntonin,  41 

T. 

Tartar,  231 

analysis  of,  233 
Taurine,  66,  140 
Taurocholic  acid,  72 
Teeth,  153 

composition  of  at  different  ages, 

155 
composition  of  in  the  two  sexes, 

156 
effect  of  putrid  food,  &c.  on,  156 
of  an  ox,  155 
porcelain,  history  of,  487 

preparation   of    mate- 
rials for,  488 
Tin,  394 

alloys  of,  400 


Tin,  borate  of,  403 

bromide  of,  402 

chlorides  of,  401 

geographical  distribution  of,  394 

iodide  of,  402 

metallic,  396 

metallurgy  of,  395 

nitrate  of,  403 

oxides  of,  397 

phosphate  of,  403 

phosphuret  of,  400 

purification  of,  396 

sulphates  of,  402 

sulphurets  of,  399 
Titanic  acid,  480 

preparation  of,  482 
Titanium,  480 

ores  of,  480 
Tonsils,  concretion  of,  234 
Ti'ommer's  test  for  grape-sugar,  97 
Troostite,  485 
Turf,  364 
Type-metal,  407 
Tyrosine,  56 

U. 

Uranite,  483 
Uranium,  oxide  of,  483 
Urea,  59 

composition  of,  60 
formation  of,  63 
hydrochlorate  of,  60 
in  the  blood,  62 
nitrate  of,  60 
oxalate  of,  61 

physiological  relations  of,  62 
quantitative  estimation  of,  61 
secreted  by  gastric  glands,  132 
tests  for,  61 
Uric  acid,  68 

in  fevers,  70 

gout,  71 
physiological  relations  of,  70 
products  of  the  decomposition 

of,  09 
relations  of  to  oxidation,  71 
tests  for,  70 
Urine  pigment,  103 

Urobenzoic  acid.     (See  Ilippuric  Acid.) 
Uroerythrin,  104 
Uroglaucin,  104 
Uroxauthin,  104 
Urrhodin,  104 


Valerianic  acid,  78 
Vomited  matters,  148 


616 


INDEX. 


W. 

Water,  its  use  in  the  body,  118 

Wood,  as  fuel,  262 
ashes  of,  264 
loss  of  heat  in  green,  263 
specific  gravity  of,  263 
ultimate  composition  of,  264 
■water  in,  2G2 


X. 


Xanthine,  63 


Zinc,  387 

alloys  of,  391 
borate  of,  394 
bromide  of,  392 


Zinc,  carbonate  of,  394 
chloride  of,  391 
dithionate  of,  393 
fluoride  of,  3^92 
iodide  of,  392 
metallic,  388 
nitrate  of,  393 
oxide  of,  390,  485 
perchlorate  of,  393 
phosphate  of,  393 
phosphuret  of,  391 
purification  of,  388 
sulphuret  of,  390 
sulphate  of,  392 
sulphite  of,  393 


THE  END. 


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